Click on your picture in the navigation bar and select Account Settings.
Select Payment Methods from the list on the left to view your saved payment methods or add a new one.
If you have multiple credit cards on file, change your primary payment method by clicking on Set as primary for the one you want.
To add a new payment method, click Add New Payment Method.
Complete all of the fields in the window that opens and click Add Payment Method to save it.
If you have an outstanding balance and add a new payment method, the outstanding balance will be charged to the card you just added.