The first step is to add your charging items in the Google development console
In this example I am using one time payment not subscription. I am using a donation example here
The main important info is the Product ID.
In your Thunkable app, enter the same product ID in the IAP component.
In your code (using a button or any kind of option) you will have to first inquire about the list (this is mandatory for Android)
I’m here using Alert component for testing purposes.
This should make it for a one time payment.
You need to publish the app to be able to see the results.
I hope this makes it a bit clearer now.
[Note]
This works for item payment or single payment but this procedure does not work for subscription payment. I have not yet tried the subscription payment method.