Adding a new payment method
Edited
To add a new payment method, go to your Buyer portal. From there:
Click on the profile picture in the top right
Go to Account
Click on Payment Methods
Go to Manage and add the payment method you want to use
Please note that if you've added a new payment method, it will not automatically update any existing repayments. To change the payment method for an existing order, you'd need to go to that order and change the payment method.