To manage your cards on file tap on the menu box in the top left of your screen, then click the menu item labeled ‘Cards’. This will bring you to a running list of all of your credit cards. From this screen you can add additional cars by tapping 'Add a Card'. If you forgot your wallet pin, tap on 'Reset Wallet Pin'. This will delete all of your current cards on file and prompt you to reset your pin.
Tapping an individual card will bring you from the following screen. From here, you can set this card to be your default card (each time you pay a tab it will use your default) or delete a card if you no longer wish to have it in your wallet.