Mike,

To my knowledge, once the car is locked the alarm is armed. I could be wrong as I purchased a Viper alarm system right away, with key FOB etc. They now work in concert and it's always armed when I lock it up, same as it was before the Viper.

There is no special key, just the ignition/door/trunk key. When the alarm goes off, the head lights should blink and the car horn sounds.