1. From your account page, click on the Manage Subscriptions tab from the Dashboard sub-menu on the left-hand side of the page. This will bring you to the All Subscriptions page, giving you an overview of your current, active subscriptions.

2. Locate the subscription that you would like to make adjustments to, and click on Subscription Details. This will bring you to that specific subscription page.

3. Scroll down on this page, and locate the Your Subscription Details options, directly below the Subscription Settings sub-menu on the left-hand side of the browser window. Click directly on the Shipping Address or Billing Address option. 

4. Update your payment details in the menu that pops up on the right-hand side of your browser window. After you have made your changes click on Add Address. A green dialogue notification will confirm that this change was successful at the top of the window. Changes to address may also be made directly from your My Account page in the Dashboard menu on the left-hand side of your browser window. From here, you may add a new address or edit an existing one.