On the Store dashboard, you'll fill out the in-app purchase details before you submit. All that info will then be in the Store database when the testers get your app.
To be specific, when uploading your app you'll take whatever information you've been using from WindowsStoreProxy.xml and paste it into the app description page. If you want to see what this looks like, go ahead and create an app package now, and then upload to the dashboard. This will then allow you do go to the description page where you can see what will be required. Just make sure to upload a new package before you complete the submission.
Also be sure to change CurrentAppSimulator to CurrentApp (you'll fail cert quickly if you forget).