How to activate your payment method in backend

Hi everyone, we are trying to build a public App, to add a payment method. The Payment method is showing in the backend but we are not able to activate it (see image below). Can anyone help with this? I understand that until the app is approved by Shopify, we can’t activate the method but how do we test it then submit it for approval. Kind of a blocked road here for us, any help is appreciated.

Thanks