To change your payment information, first log on to your account. Once you've logged on, click on 'Account Info' in the top-right corner of the home page. From there, click the third tab from the left, 'Payments & Account Credits'. Once on this page, you can add a new card by clicking on 'Add Credit Card' in the upper left of the tab, or you can edit an existing card by locating the 'Edit Card' button associated with the existing card. Once finished, be sure to press 'Save Card' at the bottom of the page.
To change the payment method assigned to specific shipping programs, you can navigate to the 'Active Programs' tab. On the left side of each program, you can select the preferred payment method from the 'Payment' dropdown menu.