In order to ensure that only customers who have purchased that specific product can leave a review on it and to ensure that they can only publish one review for the same product, you have to:
1. Enable the option “Limit multiple reviews” in the plugin settings panel.
2. Go to “WooCommerce > Settings > Products” and enable the option “Only allow reviews from “verified owners”.
If everything has been configured correctly, each review left will be marked as written by an actual customer.