Navigate to the Menu and click on Site Settings.
Click on the Available Features link near the top of the page.
Click on the Activity Ratings option*.
Click on the On/Off toggle to turn Activity Ratings on.
Click on the Save button.
Click on Confirm in the popup window.
*If you are unable to find Activity Ratings in the Available Features section, you will find it in Manage Features instead.
This means that Activity Ratings is already enabled on your LMS. If you would like to disable it, simply click on the option and use the toggle switch (as shown above) to turn the feature off.