If you have started to accept a new payment method or even if you want to split card types (Amex/Credit/Debit) you can do so by:
Click on Admin in the right-hand menu.
Ensure that you are at the organisation level but selecting "Organisation" in the drop-down just below the page title.
Click "Settings" in the Organisation Settings box.
Open "Payments"
Add new payment type and name it
Scroll to the bottom and Save