You should see two slots where you will need to insert the flat screwdriver. Once you insert the screwdriver in this slot, twist it slightly, and the shell will open. Do the same for the other side.
Next, you will notice that only part of the shell is separated. Insert the screwdriver on the edge of the shell and twist it again. This should open the shell completely. Place the back Mazda key fob case aside.
Remove the key fob battery cover from your Mazda remote.
Pull out the dead key fob battery from the Mazda keyless remote.
Insert the new battery. Make sure the positive (+) symbol is facing you. The positive is on top, while the negative side of the button cell battery is facing the key fob.
Insert the O-ring in its channel if it came off during the earlier step when you removed the battery from the Mazda remote. Press the battery cover in place
Press the two key fob cases together until you hear the shells click and lock in place.
Press the metal (emergency key) into the Mazda key.
Test the key to ensure that the remote is working properly.