Product reviews allow you to claim yellow stars on your products in Google Shopping. To set this up you need a "product review feed" according to Google's specification. We automatically create this for you. When your first product reviews have come through us, you can have them sent to Google. You will find the feed under Reviews > Product reviews > Settings (cog wheel next to Product reviews), here you will find a button"Get Google Feed".
At Google, you can read exactly how to upload this feed within your Merchant Centre account.
The review data in a feed for product reviews is linked to your products based on a number of factors. Globally unique product IDs such as GTINs (Global Trade Item Number, EAN for Europe) are most important for this. If no GTIN data is available, Google tries to link reviews based on other metadata, such as SKU, product URLs and combinations of brand and MPN (Manufacturer Part Number). These IDs usually do not provide a good link. This means that without GTIN/EAN, you may not see star ratings on the products you offer.