Apple iMac (21.5-inch and 27-inch, Mid 2011) - Manual (Page 12)

12 Chapter 1 Ready, Set Up, Go
Step 3: Turn on your wireless keyboard and mouse.
Press the power button on the right side of your Apple Wireless Keyboard and slide the
switch on the bottom of your Apple Magic Mouse to turn them on.
Your wireless keyboard and mouse come with AA batteries installed, and they’re
already paired with your iMac. Pairing allows them to communicate wirelessly with
your iMac.
Power button Indicator light
Indicator light On/off switch
When you first turn on your keyboard or mouse, the indicator light glows steadily for
5 seconds, indicating the batteries are good. If your keyboard or mouse doesn’t turn on,
make sure batteries are installed properly (see “Replacing the Batteries” on page 56).
The indicator light blinks until you turn on your iMac and a connection is established.
Note: If you purchased a USB keyboard or a USB mouse, connect the cable to a
USB port (d) on the back of your iMac.