Most apps support app-block install for reviews widgets.
To display ratings and reviews properly in our Shopify themes, a standard metafield is used. If your review app doesn't use this metafield, you'll need to edit the code to integrate review widgets throughout
Changing review and rating metafields
Find correct metafields
Identify the metafields used by your review app - you may have to look through app documentation or contact support.
Edit code
Open up component__rating.liquid
If you can't find a metafield from your app that points to the max value then you can manually set this. E.g. if your rating system goes from 0-5 you would set max to 5.
Update lines 29-31 to point to your app metafields. After making changes it should look something like this. The below example uses metafields from Loox.
