This can be a back up to your remote key to ensure you have TWO keys minimum to START your car.
Having only ONE key can lead to a very expensive and inconvenient time if you lose it!
This is normally a straight forward job whilst you wait.
Please note that this option is NOT available on some vehicles with alarm systems. However, many vehicles will switch off the alarm when you turn the ignition on.
Just open your door without using the remote and turn your ignition on (start the car) to see if the alarm stops!