1. Login.
2. Go to the 'My Account' link located on the top right drop-down menu:

3. Click on the 'My Subscriptions' link:

4. If your card has expired or you are changing your payment method, click the 'Edit' link next to your existing payment method:

5. Here, you may edit, add, delete, or select a new payment method:
Note: You must select your new payment method before deleting the existing method.