This article explains how to add your existing payment details in Ordermentum to a new supplier:

1) If you are not there already, go to the home screen of the app.

2) Click on the cog icon in the top right hand corner of the app and go to Venue Settings>Payments

3) Under Payments select Existing Payment Methods

4) You will be taken to your existing payment details where you can then toggle on the supplier(s) you wish to use this payment method for.