Right-click on a blank spot near the top your your monitor and choose "Customize..." from the drop-down.
When the "Customize" dialog box opens go to the "Shortcut Bars" tab, choose the "Sketch" icon near the top right, select "Sketch" from the "Toolbar:" drop-down, then drag the "Mirror" icon onto the shortcut bar.
Hi,
just right-click on the menu...