How to Connect a Mouse to a Mac

Method 1 of 2:

Connect the mouse to your Mac using the Lightning-to-USB cable. Plug the Lightning end into your mouse, and the USB end into your Mac.
Flip the switch on the bottom of the mouse. You'll see a green light above it, indicating it's on.
Wait for the device to pair. Your Mac will automatically pair the mouse with your computer.
Allow the mouse to charge. The mouse will charge while it's plugged in. Disconnect it once the charge is full.
1. The Magic Mouse 2 will not function while plugged in.^[1]

Method 2 of 2:

Click the Bluetooth button in your menu bar. If you don't see this menu option, open the System Preferences menu and select Bluetooth, then check the On box.
Click Turn Bluetooth On.
Turn the wireless device on. Use the switch on the bottom to turn it on.
Click the Apple menu.
Click System Preferences.
Click the Mouse option. If you don't see this option, click the Show All button at the top of the window.
Click the Set Up Bluetooth Mouse button.
Click Continue when your new mouse is highlighted.
Click Pair if prompted. This may appear for older wireless mice.
Click Quit after your device is paired. You can now use your wireless mouse with your Mac.^[2]