To manage your billing data, go to your Company/Account settings. Make sure that your account role allows that. Choose Billing on the panel on the left.
First, choose one of the options: Company or Individual. Depending on your choice, you will have to fill in slightly different forms. Make sure your information is correct. Click the Save button when you are ready.
Choose Saved Cards on the panel on the left or just scroll a bit further. Here you can add a new card and see what cards are already used if any.
Please make sure your information is correct, then click the Add card button.