Right click anywhere on your desktop and select Personalize
. Alternatively, you can navigate to:
Control Panel\Appearance and Personalization\Personalization
A new window should come up either way. Now, in the bottom right corner, there should be a screensaver section. If there is a red circle over it, and below it it says none, your screensaver is turned off.
To turn it on, click on the screensaver icon and out of the new window that pops up, select the drop down menu.
Choose your preferred screensaver and click Apply
Your screensaver should now be turned on. If you require more assistance, feel free to go through the following tutorials. They should contain step by step instructions on how to both change and turn on/off your screensaver. Screen Saver - Turn On or Off Screen Saver - Change
Hope this helps,