Head to the Desktop mode by pressing Windows+D or clicking the Desktop tile.Right-click on an open space on the desktop and go to New > Shortcut.In the location field, type shutdown /p and then click Next, then Finish.Right-click on the new shortcut and choose Pin to Start.
If you like, you can also create a reboot tile using shutdown /r /t 0 (zero, not the letter "o" at the end) in step 3.