To update you credit card information go to "Settings & Plans" from the main menu, then choose the "Billing History" tab. Then click the link "Update Credit Card Info".
If the "Update Credit Card Info" is not available please sign out and sign back in. The link or option should now appear. If it doesn't please contact us at email@example.com or click "I did not find this information helpful" on this FAQ page to open a support ticket.