All you have to do is disconnect and reconnect the negative battery terminal. You need only disconnect for about 15 seconds , no more.

Be careful when re-connecting it as the horn sounds, it will scare the hell out of you but your alarm will work again after this.

This is THE ONLY post in this thread that will work for you

Don't listen to these other folks that appear to be pulling your leg or have no idea what they are talking about!

Enjoy your new ride!