Windows 8.1 allows you to use Screen Saver to protect information and secure the tablet or computer after the display is off for a specified time. While its Password Protection has been turned on and the device wakes from sleep or hibernate, you need to type a password to to unlock it. To do that, make sure you have created the password for the user account that you are currently logged in as.
How to enable password prompt for screen saver in Windows 8.1
Through PC settings on tablet
* On Start screen, click on the down arrow button at the bottom left corner, click on the “PC settings”
* Select the Accounts > Sign-in options
* On the right side, choose how long after the display(s) from the list under Password policy, such as Always require a password, 1 minute, and 15 minutes.
* Press Win + R from the keyboard, and input any of the following commands:
Rundll32 shell32.dll,Control_RunDLL desk.cpl,,1
and press Enter.
* Within the screen saver setting, check “On resume, display login screen” box, select the waiting time and the screen saver you want to use.
* Clcik Apply > OK button to apply all changes.