How to Customize the Windows 8.1 Interface
Click the Power & sleep option.
The settings enable you to choose when your screen turns off and if you want to have your PC go to sleep after a specified period of time.
If your PC goes to sleep, none of your apps will run while the PC is sleeping, so you won't receive any e-mail messages until your PC wakes up again.
After you've finished making your PC & devices choices, click the back arrow to return to the PC settings screen.