Step 1: On the bottom menu, select the profile icon on the far right hand corner. From there, click into PROFILE SETTINGS.
Step 2: Select PAYMENT INFORMATION.
Step 3: You can switch between alternative stored payment methods, or select the '+' on the top right hand corner to add a new payment method.
IMPORTANT: To remove an old expired method of payment, you must add a new payment method first, before removing the old.