You can update your credit card from the billing section of your dashboard, just click "Link New Card" and fill out the requested information.
Once you've added the card, select the red box ("Select Method") in the Active Combines section. Select the new card and click "Change Payment Method". Once you've successfully linked your new card to your active Trading Combine, you will see a screen that says "Payment method has been successfully changed." You're all set!
You can remove a credit card directly from the "My Profile" section of your dashboard. Just click "Billing," click on the card you'd like to remove → Edit → Remove Card → Continue. The card should now disappear from your dashboard. Please keep in mind that you will need to have a credit card on file for any future active Trading Combine® accounts.