UE4 how to make in-app purchases with google pay?

Hello. I am still beginner with ue4.
I have almost finished a video game and I would like to integrate in-app purchases with payment by Google pay.
Can someone tell me the procedure to follow (or a video or a tutorial)?
It’s been a while that I look but without finding anything very satisfactory.

Hi,
Using IAP on Android. documentation

Hello. Thank you for your reply. I read the documentation but I can not understand.
I want to sell items through my game. But I do not know how to make the link between the items and the credit card users or method of payment users.
For example, how to integrate Goolgle Pay?

Any progress?