(credit to Mihai-Emilian Blaga for original larger article)
How To Open The Screensaver Settings Window
If you want to customize the screensaver, first, you need to open the Screen Saver Settings window. In order to do that, right click or press and hold the Desktop and select Personalize from the contextual menu.
NOTE: Alternatively, you can open the Control Panel, go to Appearance and Personalization and then Personalization.
In the Personalization window below the list of themes, click or tap the Screen Saver section.
The Screen Saver Settings window opens.
How To Change The Active Screensaver
To select a different screensaver for your Windows theme, click or tap the Screen saver drop-down list. Then, select the new screensaver that you want to use.
If you don't want to use a screensaver, select (None). This is the equivalent of disabling the screensaver for the active Windows theme, and will leave your unattended computer open to passers-by.
How To Configure The Active Screensaver
In the Wait box you set the number of minutes of inactivity after which the screensaver is started.
Also, you can set whether to display the logon screen when you resume using your Windows PC or device.
This feature helps prevent passers-by from tampering with your unattended computer, email and other data. We recommend you leave it on.
When you've adjusted settings to your liking, click or tap OK to apply your settings.
Conclusion
As you can see from this tutorial, setting the screensaver in Windows 7 and Windows 8.1 is relatively easy. As long as you know where to look for the screensaver settings, any personalization can be done in a matter of seconds.