How to re-pair a bluetooth mouse device that has already been paired

How to re-pair a bluetooth device that has already been paired 

1. Turn off the trackpad by holding down the power button until the light goes out.
2. Turn on the trackpad by pressing the power button, and keep the power button pressed until it is paired. The light on the mouse will start blinking, it will show up in Bluetooth Preferences, and you will be able to pair it almost immediately so long as you do not let go of the power button from the moment of turning it on until after the trackpad is paired.