You need MetaMask
MetaMask is a crypto wallet & gateway to blockchain apps. Download and create an account.
At the top you can see your actual network, click on your actual network and switch to a test networks like Göerli (it will be the same principle for Rinkeby).
When you have switch to a test network, copy your wallet address and go to Chainlink. Past your wallet address and click on the send me 0.1 ETH button.
Now, go back to MetaMask and…
There you go, you can now spend your $300 of ETH to test your projects like NFTs 🔥
PS : you can repeat the process to earn more