Once you have logged in, navigate to the Billing page in the Account drop-down at the top right corner of the page. On this page, there are two sections: My Plan and Billing Details. The name associated with your billing credit card and its last 4 digits are displayed under the Billing Details section. Click on the Change Card button and enter in your new credit card details. When you are finished, click Save and your credit card is updated. This new card will be charged at the beginning of your next billing period.