Note: You will need a small flathead screwdriver.
Find the notch at the bottom corners of the device.
Using the screwdriver, pry off the cover of the device.
Remove the plastic cover and gently remove the circuit board from the rubber cover.
Gently remove the battery.
Note the battery terminals (+, -).
Place a new battery in the device (CR2032).
Place the rubber cover back on the circuit board, ensuring the corners match up, and place it back in the plastic cover.
Press in the two sides of the plastic cover until you hear a click.
Test the buttons. If the device is functional, the light will blink when you press a button.