GALANT ALARM PROBLEM?

I have just had my 2002 Mits Galant fitted with LPG. When i picked it up the alarm sounded when ever i try to set it. I have been told to reset the alarm but i believe you need a pin for the resseting procedure which i dont have. can someone tell me where the "brain box" of the system is so i can get the serial number off of the side. Or how i can fix the problem. thanks

    I got a 2003 model last week.
There was a card in the document wallet that had the details on it.