If you selected a signup offer when you first signed up for 'Tap & Pa$$', you'll usually find it on the 'deals' tab:
Note that some signup offers may only be valid for a limited time.
Some signup offers are for a fixed amount PA$$BUCKS - if you selected one of these the amount will be added directly to your PA$$BUCKS balance for that vendor.
Also, check out How do I redeem a deal?