What is OpenSea? 

OpenSea is an online marketplace built on the Ethereum blockchain. It is the leading place to mint, buy, and sell Non-fungible tokens (NFTs) on the Ethereum blockchain or polygon sidechain. OpenSea also supports NFTs on the Klatyn blockchain; however, it is less commonly used.

Because OpenSea is a peer-to-peer Ethereum-based market, users need Ether (ETH) coins to pay fees associated with minting and trading NFTs.

In this tutorial, we'll go over how to link up a wallet to OpenSea as well as how to mint, buy, and sell NFTs on the platform.

Getting set up

Start by heading over to 'opensea.io'. OpenSea also has a smartphone app that you can use, but for this tutorial, we'll be working off of OpenSea's webpage.

As mentioned, you'll need some ETH coins to do anything on OpenSea.

You can buy ETH coins from exchanges like Binance or Coinbase. If you don't already have an account with one of these exchanges, then you will need to set one up. We have a beginner’s tutorial on Coinbase coming out soon, so keep an eye out for that. 

Once you have this done, the next thing you'll need to do is connect your wallet to OpenSea. Your wallet is where you can store your ETH. Because OpenSea is a peer-to-peer marketplace, you'll also need your wallet to facilitate transactions on the blockchain.

The wallets that OpenSea supports include MetaMask, Coinbase, and Trust wallet. MetaMask is the one that the majority of people use. If you don't already have a MetaMask, then take a look at our MetaMask for beginners tutorial linked here.

It's also possible to directly add ETH to OpenSea via the 'MoonPay' payment option; however, this ends up being more costly, so we don't recommend it.

To link up your MetaMask wallet to OpenSea, all you have to do is click on your profile icon in the top right-hand corner of the screen and then click 'My profile'.

You’ll then be brought to the sign-up page for your wallet, where you will be prompted to complete a few simple steps. When your wallet is connected, your screen should look something like this:.

To personalize your profile, select the gear settings icon towards the right of the screen. Here, you may be required to 'Sign' an additional security prompt.

Following this, you'll be able to create a username and bio and enter an email address for your account.

Buying Ethereum-based NFTs

Back on OpenSea's homepage, if there's a specific NFT drop that you're after, then simply type in the name of the NFT in the search bar.

An important thing to watch out for is whether or not the NFT you're interested in has a blue tick. This means that this NFT has been verified (i.e., is legit). 

You can also browse for NFT's by clicking on the 'Explore' tab and choosing whichever category you'd like to search through.

As you are browsing through NFT collections, you’ll notice that to the left of the screen, you have a filters tab. An important feature of this section is the 'chain' filter, which allows you to refine your search based on whether the NFTs are Ethereum, Polygon, or Klaytn-based.

When you click on an NFT that you're interested in, you'll be able to see more information on the NFT, like its description, properties, price history, how many views it's had, and whether it's being sold via a timed auction or being sold at a fixed price.

If you want to buy or make an offer on an NFT, you first need to make sure you have the right type of ETH, which is what the NFT will be valued in.

If there is a grey icon beside the price of the NFT (like the one in the image above), then it is valued in standard ETH, which is generally used when an NFT is not being sold by a timed auction. As long as you have enough ETH in your wallet, you can go ahead and click the 'Buy now' or 'Make an offer' option. The first time you use a particular cryptocurrency on OpenSea, you'll be asked to approve the transaction.

If there is a pink coloured icon like in the image above, the NFT is valued in what is called 'wrapped ETH' (WETH).

With WETH, it is possible to carry out transactions with a time delay, which is what enables auctions to take place on OpenSea. In other words, when you place a bid in an auction using WETH, it will be held until the auction is finished. If you win, then the transaction will go through, if you don't, the transaction will be cancelled, and the WETH won't be taken from your wallet.

ETH and WETH are equal in value, and converting ETH into WETH is simple. All you have to do is click the wallet icon on the top right corner of your OpenSea homepage, select the three dots next to your ETH balance, and then choose 'Wrap'. 

Enter how much ETH you want to convert. Once you're happy, click on 'Convert tokens'. After you sign the transaction, the WETH should be visible in your wallet.

Sometimes your WETH may not appear right away. If that happens, you might need to manually add WETH token support to your MetaMask wallet or whichever wallet you are using. In MetaMask, this can be done by clicking 'Add token' on the homepage of your wallet.

Once you have your WETH, you're now good to place your bid!

Note: ETH and WETH are the most common currencies used on OpenSea, but other tokens such as USDC and Dai are also supported. Each time you use a cryptocurrency for the first time on OpenSea, you will be charged a one-time token approval fee.

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Buying Polygon-based NFTs

The gas fees (i.e., transaction fees) that come with minting and trading on the Ethereum blockchain are often very high. Because of this, a lot of people mint, buy, and sell NFTs on the Polygon side chain instead. 

Polygon is a layer 2 solution that facilitates instant yet secure transactions using ETH tokens. Unlike the Ethereum blockchain, there are no initialization or gas fees on the Polygon blockchain. 

In order to use Polygon on OpenSea, you'll first need to 'bridge' or transfer over some ETH to the Polygon blockchain. 

Start by clicking on the wallet icon on the top right side of your home screen. Provided that you have already added some ETH to your wallet, click on the three dots beside the 'ETH' icon.

A 'Convert tokens' page should then pop up. Next, type in the amount of ETH you want to transfer over to Polygon. Keep in mind that each time you bridge some ETH, you'll be charged a flat ETH gas fee. 

Once you are happy, click 'Convert tokens'. OpenSea will then prompt you to sign the transaction. Following this, you should receive confirmation that the transaction was successfully processed. Bridging tokens can take between five and ten minutes to complete. 

When you view your wallet, you should now be able to see your polygon, ETHPolygon, indicated by a purple icon. You are now ready to buy a polygon NFT! 

Note that the first time you buy an NFT on the Polygon chain, you'll be prompted to 'unlock Polygon trading' on your wallet. 

How to Mint an NFT on OpenSea

To mint (create) an NFT collection, start by clicking on your profile icon on the right side of your homepage. Next, select 'My collections' followed by 'Create collection'.

On the next page, you'll be able to add a logo image, a featured image, and a banner image for your collection. You'll also need to add other information, like the collection's name, a brief description, and any social media links related to the collection.

Towards the bottom of the page, you have the option to add a 'percentage fee', otherwise known as royalties.  This is a payment that you'll receive each time your NFT is resold on OpenSea. A percentage fee of five percent is considered to be quite reasonable.

For your 'payout wallet address,' simply copy and paste in your Ethereum wallet address found in your MetaMask wallet. After this, you can choose which blockchain you want to list on as well as the payment token.

Once you have filled everything out, click 'create', and you will have made your NFT collection!

To begin adding items, click 'add item' on the right-hand side of your collections homepage.

Next, you'll need to upload your NFT file, give your item a name and a brief description.

To help make your NFT stand out, you can also add more details in places like the 'properties' and 'levels' sections.

Once you click 'create', your NFT will have been minted!

Selling an NFT

To sell your NFT, click on your profile icon and then select 'my profile'. Click on the NFT you want to sell.

Click 'sell' in the top right corner. Next, you'll need to decide whether you want to sell your NFT at a fixed price or if you can sell via a timed auction.

If you choose to sell at a fixed price, the buyer will pay any associated gas fees. In the 'privacy' section, you have the option to reserve your NFT for a particular wallet address, so it's almost like a reserved auction.

If you decide to sell by auction, you can either sell to the highest bidder (an English auction), or you can set a price that will decrease until someone buys your NFT (Dutch auction).

Should you choose to go with an English auction, you'll have to decide on the starting price and duration of the auction. If the auction ends with the highest bid being over 1 ETH, then you won't be charged any gas fees. If the accepted bid is below 1 ETH, then you will be charged gas fees.

When selling by Dutch auction, you have the option to set a fixed reserve price. This means that you can start with a high initial price that will decline over a certain time period, where bids can be placed at any time. If the auction concludes with an offer that is lower than your reserve, you have the option to either accept or reject that bid.

Note that the first time you sell on OpenSea, you'll be charged a once-off account initialization fee to list on Ethereum. Also, if the NFT you are looking to sell was not minted on OpenSea, you'll be charged a once-off approval fee. OpenSea also charges a 2.5 percent transaction fee for all sales 

Select 'place your listing', and you're good to go!

When you receive an offer, always double-check that the offer is in the correct currency that your NFT is valued in.

Disclaimer: THIS IS NOT FINANCIAL OR INVESTMENT ADVICE. Only you are responsible for any capital-related decisions you make, and only you are accountable for the results.