When you created the account, you likely setup a monthly (or yearly) auto-renewal to pay for the fees. If you need to update the billing information on file, you can do that right in your account.
Navigate to Administration - Billing Information. Make any updates and click Save. When your next auto-renew cycle comes up, then it will be charged to this new account information.
Important! If you received a notice that the account renewal failed, then you'll want to update your billing information by going to the Extend Account link under the Administration tab. This will automatically update your credit card on file AND renew the account until the next billing cycle (either monthly or yearly)