To use your iMac, you need two accessories included in the box—the Magic Keyboard and the Magic Mouse 2.
Important: To begin using your Magic Keyboard and Magic Mouse 2, simply make sure the on/off switch of each device is on System Preferences, click Mouse, then click the buttons at the top to see all the scrolling, clicking, swiping, and tapping options.
If you configured your iMac with the optional Magic Trackpad 2 or Magic Keyboard with Numeric Keypad, it comes connected with your iMac and ready to use. If you purchased a Magic Trackpad 2 or Magic Keyboard with Numeric Keypad separately, connect it to your iMac with the included Lightning to USB cable to connect with it using Bluetooth. Use this same cable to charge your devices as necessary, then unplug them and use them in the location that works best for you.