In order to sell your first NFT, you’ll need to enable OpenSea to sell items from your account. This requires a blockchain transaction, so you’ll have to pay a gas fee. Send some Ether to your MetaMask, and you’re good to go. You’ll only need to pay this fee the first time you create an NFT collection.
If you don’t have any Ethereum, you can use Coinbase or Gemini to purchase some and send it to your MetaMask wallet. If you’re completely new to cryptocurrencies, it may be useful to start with Benzinga’s guide to buying Ethereum.
Now that you’ve given OpenSea permission to sell your NFTs, anyone can find and purchase them on the OpenSea marketplace. You’re done!