The contract address is the 16-digit hex code specific to where all of the code that powers the token is placed on the blockchain.
Go to Etherscan.io.
Search for the token that you would like your user to hold to access the content.
3. You will be directed to the token summary page. On the right-hand side of the, under Profile Summary, under Contract, you will see the hex code.
For example, here is an example of the DAI summary page on Etherscan:
Go to the marketplace that the NFT or asset was minted on.
Search for the chain info.
For example, on OpenSea, on the webpage of the NFT, you can find a section labelled as "Chain info" which lists out the contract address and token ID.