Pinata website can be used to upload assets, but a script is also provided for convenience.
After following the steps in the guides above, you'll receive a baseTokenUri for your project. This way, the contract knows how to associate each token ID with an individual token URI without having to send the contract a list of URIs. All token URIs can be determined by appending the token ID to the base URL.
Be sure to update your config.js with this baseTokenUri.