The Ratings and Reviews feature (where you see the star rating on the main Facebook page) is available when your page is categorized as a Local Business and has a physical address. By default, reviews and star ratings are displayed. However, you can change this setting if you’re in the Local Business category and don’t want to show your ratings and reviews.
To make sure this feature is enabled, go to the About tab, find the Address section and click Edit next to the address. You’ll see a map with your address. Check the box next to Show Map, Check-Ins and Star Ratings on the Page.