Click the "Billing" section on the left-hand side.
Here you'll be able to add a new payment method, update the expiration date on your card (if you have a new card with the same number but different expiration), or update your mailing address.
IMPORTANT: If you update your billing method by adding in a new payment method, it is imperative that you Edit the assigned profile.
To do this, the locate your list of Recurring Transactions on the Billing Information page (where payment info is added/updated). Click on Edit on this page to change the recurring donation's assigned payment method to the NEW payment method. This does not happen automatically.