First off, I would try the12volt.com or something else as this forum is dedicated to installing mp3 playing devices into cars for entertainment systems, not so much alarms.
Second off, I have installed several DEI systems several years ago. There are 2 different transmission modes, manual and auto. In manual, you have to "initialize the system" before you get out. Basically, when you arrive at your destination, with the engine still running, you initialize the remote start from the keyfob. It realizes the car is still running so it doesn't turn the starter. Now you can take the key out of the ignition. Then you get out of the car and lock the doors using the fob. Then I think you stop the engine using the remote start button. This allows the system to know "for certain" that your car is not in gear and it is initialized to remote start itself at a later time so long as you don't unlock the doors (thus allowing you to accidentally put it in gear).
All that to say, you need to program it for automatic transmission and you won't have to do this anymore. The book that comes with it will tell you how to do that. I can't remember off the top of my head as it has been years.