Apple iMac (21.5-inch and 27-inch, Mid 2011) - Manual (Page 58)

58 Chapter 4 Problem, Meet Solution
To replace the batteries in the Apple Magic Mouse:
1 Slide the on/off switch on the bottom of your mouse to turn it off.
2 Slide the latch down and remove the battery cover.
Latch Batteries
3 Insert the batteries with the positive ends (+) facing up, as shown above.
4 Replace the cover and turn on your mouse.
You may have to click your Apple Magic Mouse once to reconnect it to your iMac.
To check the battery status, slide the on/off switch to turn on the mouse. If the
indicator light doesn’t glow, you may need to change the batteries. You can check the
battery level in Mouse Preferences. Choose Apple () > System Preferences and click
Mouse. The battery level is shown in the lower-left corner.
Problems with Your Internet Connection
The Network Setup Assistant application on your iMac can help walk you through
setting up an Internet connection. Open System Preferences and click Network.
Click the “Assist me” button to open Network Setup Assistant.