Follow these simple steps:
Log into your web browser.
Click your profile picture in the top right.
Head to 'Billing'
Head to the payment methods tab.
You'll see the options to add new cards and make changes to cards already linked to your account.
To clarify, the update button only allows you to update the billing address. To change / add a new card, please press 'add new payment information'.
If you're a client on a subscription based program, the system will automatically attempt to make payment from your new card (assuming set as default).
You'll also see the ability to add your billing information. This information will appear on all invoices and receipts after you've added it.
Thanks
FITR