Hi @Click2Graph
You will want to follow the steps listed on:
In-app purchases and trials
https://learn.microsoft.com/en-us/windows/uwp/monetize/in-app-purchases-and-trials
Enable in-app purchases of apps and add-ons
https://learn.microsoft.com/en-us/windows/uwp/monetize/enable-in-app-purchases-of-apps-and-add-ons
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If this is helpful please accept answer.