Remove the mechanical key from the fob by pressing the release button
Locate the seam or slot on the key fob
Use a small flathead screwdriver or coin to gently pry the fob open
Separate the two halves of the fob
Remove the old battery
Note the battery type and orientation
Insert the new battery with the correct polarity
Snap the fob halves back together
Reinsert the mechanical key
Test the key fob buttons to confirm it works