In the Debut theme, there's a 'Custom Content' section you can add, then add a Custom HTML content section and paste something like Android App to manually link. In a rare case, you might have to add actual HTML to get it to work.For 'Rich Text' fields, you can usually find a chain link icon at the top that works similar to the page editor mentioned above.If you click Online Store, then Theme, you can customize your home page. If you want it on your home page, it might depend on your theme how easy this is to do.You can repeat the process for the Apple store. The page should now link to the play store.Copy the play store link and paste it as the URL, then hit Save.Highlight the Android text and click the link icon (it looks like 2 chain links).In the editor, type something like 'The app is available for Android or Apple device.'.Add or edit a page in your online store.Create a page on your store about the app, and embed links to play/ios.Adding a product to your store that links to the Play/App Store, which I don't think is possible.I can think of a few ways you might do this: