Invision Community allows your user to rate any item in your community. One can rate topics, products, or page contents. Unfortunately, the rating stars are very inconveniently placed above the content. The most users would not scroll up to rate the content after reading it.
If you enable rating (not reviews!) in a FX Pages database, the rating stars are displayed prominently below the content. At the place where the user is ready with reading and can rate it in passing.
To enable ratings in a database, check database (category) settings and group permissions.
Go to your AdminCP and open Members -> Groups. Edit all member groups, that should be able to give rating on the tab Content.
If your database does not use categories, open the database for edit in Pages -> Content -> Databases and Enable Star Ratings.
If your database does use categories, go to Pages in AdminCP and click on Categories. Edit each category, that should allow ratings and Enable Star Ratings for it.