What's an NFT?
A Non-Fungible Token (NFT) is a digital file whose unique identity and ownership are verified on a blockchain (a digital ledger). All of my NFTs are minted on the Ethereum blockchain and can be stored in your Ethereum wallet.
How do I buy an NFT?
First, you need an Ethereum wallet. A popular one is Metamask, because it has a Google Chrome plugin. Once you install Metamask and create a wallet, you should send some Ethereum to it. If your not sure where to get some, here is a list of places that sell ETH.
My NFT's will be listed on OpenSea, the largest NFT marketplace. You can sign-up for OpenSea with your Metamask wallet.
To make transactions on the ETH blockchain, the network requires a fee (gas) that can vary depending on how busy the blockchain is. The first time you attempt to make a transaction on OpenSea (buy, make an offer..) you will have to pay some gas to give OpenSea permission to send ETH from your wallet. After you complete this transaction, you are able to buy NFTs!
For more info, see this guide from OpenSea