How to Turn On a Keyboard on an iMacby Christina Hadley ; Updated February 10, 2017
The generation of iMac computers introduced in 2011 comes with some new features, including a wireless Magic Trackpad and sleek aluminum keyboard that operates without a physical connection to the iMac. Although these components don’t require physical wiring, they still need a source of power. Ensure your wireless keyboard has the power it needs when the keyboard's green light is not illuminated.
Turn on the iMac. Press the power button on the keyboard. Apple pairs the wireless keyboard with the iMac for your convenience. All you need to do is turn on the computer and keyboard – the devices should interact automatically. When the iMac is on, you will know there’s a problem if the keyboard remains off after you press its power button and the green LED fails to illuminate.
Pair your keyboard with the iMac if the keyboard's green LED is blinking – that’s an indication that the keyboard is in discoverable mode and needs to be “paired” with the iMac. Open your "System Preferences" menu with your mouse and select "Keyboard" in the "View" menu to set up the Bluetooth connectivity, if necessary. Then, press the power switch on the keyboard to see if the device will remain on.
Replace the keyboard’s batteries to restore its functionality. If the keyboard's power switch has no effect, even though the computer is turned on and paired with the keyboard, inserting fresh batteries may correct the problem. Find a coin that fits into slot on the keyboard's battery compartment cover and use it to unscrew the cover, turning counterclockwise. Slide the expired AA batteries out and replace with fresh batteries, making sure you insert the positive terminal of each battery first. Close the battery compartment cover by screwing it back on.
Press the keyboard's power switch after installing fresh batteries and look for a solid green light. If the LED illuminates, your keyboard is on and ready to use.