You can enter new credit card information only if you have a payment pending for an event.
Note: If updating an expiration date, or your billing address you must first add a new card and then go back to remove the old one.
- Billing Tab → Outstanding fees → Change Account
- Pay by Credit Card Tab→ Enter card info
- Complete Registration
There is no way to add or edit a credit card to your account without having a pending payment. So if you aren't registered for anything currently, simply use the new credit card the next time you go to register.