Automotive key fobs are used to lock and unlock doors, set the alarm (if the vehicle is so equipped) and operate accessories (such as remote start). A key fob's battery may eventually run down and require replacement.
Remove the retaining screw from the back of the key fob. Open the key fob case and remove the battery cover.
Remove the old battery from the battery receptacle. Install the new battery in the receptacle, ensuring that the new battery is oriented in the same way as the old battery.
Replace the battery cover and close the key fob case. Insert the screw and tighten gently. Test the key fob to ensure that the battery replacement was successful.
Since the key fob is programmed to your vehicle specifically, no further configuration should be needed.