To change the card you delete it from your account, and when you need to pay, you'll be asked and you enter your new card info.
To delete your card:
- From the home page, Click 'My Account' (the gear on mobile)
- If you have a card in the system, there should be a 'Payment Method' row under 'login Info', click 'Manage' next to it.
- You'll be taken to the ID server and asked to log in.
- Once you Login and your account info including credit card will be displayed. Click 'View' to see your card's info.
- You'll get a box with 'Payment Info'.
- Click 'Delete Info'.
- Next time you need to pay, you'll be asked for your payment info and you can enter your new card's info.