Log into your account.
At the top of the page, click on ‘Billing’ and then click on the ‘Manage Credit Card’.
Click on ‘Add new Credit Card’ and fill in the necessary details. Once your done, click on ‘Save Changes’.
If you need to make changes to an already existing credit card, in the ‘Manage Credit Card’ Section click onto the pencil and line symbol on the right of the card you want to change.