First:

The Approval functionality is similar to the Transfer functionality, while focusing on the most needed components to complete a successful approval.

In similar fashion to the transfer process , the token contract address needs to be set to begin approving addresses to open tokens on your behalf. The search input field helps with this as if it a recognized, token on the mainnet, you can simply type the name of the token and have the token details loaded, otherwise simply providing the contract address in the contract address field will do the trick.

Use the Input to either search for known token or provide token contract address

Next:

Switching to the Approve tab is always the next thing to do, else you will be accessing the Transfer functionality and not the approval functionality.