Step 1: Go to the 'Payment methods' subsection (By expanding the 'Billing' section of the left-hand menu).
Step 2: Click on 'Add / Edit Payment Method'.
Step 3: You will then be presented with the following options:
- Cancel subscriptions (by clicking 'Cancel Subscription');
- Add a new payment method (by clicking 'Add a payment method');
- Update your billing information (by clicking 'Update Information');