The Apple iMac incorporates a central processing unit, hard drive, optical drive, speakers, microphone, camera and flat-panel LED screen into a single unit. The iMac comes with a wireless, battery-powered multi-touch mouse, which Apple calls the "Magic Mouse." This mouse has a single smooth surface; drag your finger across it to scroll through windows, click, double-click and right-click.
Click the Apple logo in the menu at the top of the iMac screen on your iMac, then click "System Preferences." Click on "Mouse" in the "Hardware" section.
Click on the "Secondary Click" checkbox to check it. Click on the pull-down menu, then click "Right" to enable right-clicking. Click the red circle at the top of the window to close the System Preferences window.
Move the Magic Mouse so the cursor is over the desktop, then press the right-hand side of the mouse to right-click. The iMac opens a menu of options, which you can highlight by dragging the mouse up or down.