Step 1: Right-click on a open area of your desktop, then go to New and select Shortcut.
Step 2: In the location box, type shutdown /p to shut down Windows 8 immediately or shutdown /r /t 0 to reboot Windows 8 immediately. Click Next to continue.
Step 3: Type a name for your shortcut, then click the Finish button.
Step 4: Right-click on the shortcut from your desktop and select Pin to Start.
Step 5: Go back to the Start screen and verify that the new tile appears.
Now to Shutdown and Reboot your Windows 8, you can just double-click on the desktop shortcut