In the newest version of the app you can verify that markup is being added to your pages by viewing the source of your page and looking for a JSON-LD block at the bottom of the page's head element.  The block of JSON-LD will be surrounded by a comment saying "SchemaAPP Liquid Start" and "SchemaAPP Liquid End".  

In the previous version of the app, the schema markup can be found in the body element of the page, also surrounded by the same comment but the JSON-LD will have more space between its lines.

To update to the newest version of the app, simply visit the app's page in your Shopify store and you will be prompted to confirm the update.