2001 Pontiac Grand am wont start?

[AlexandraK]

OK so after a few months of our car sitting, it my husbands work car, we decided to finally fix it. Well we narrowed it down to the ignition switch, replaced and did the whole security thing leave the key in for 15 min thing, once we did the car would start and then die after about 2-3 sec. So after a few tries of this, it went to nothing... I mean NOTHING! No lights no nothing. So we waited a few mintues and tried again... this time nothing but the ECU BMC... the computer thing thats under the glove box??? started clicking kind of crazy! So we checked the battery and it was bad. So off we go again... brand new battery and $80 later, we get the lights on now and they all come on in the instrument panel and everything, then click, one single click and nothing else, except this time the Check engine light comes on and stays on...... Im frustrated... tired and I can't afford to get a tow... We need to get this thing running so we can sell it for cheap and move on! Oh yes I forgot to add that we changed the oil, put in another gallon of gas and that fuel system cleaner, LOL I know super technical but hey, you get what Im talking about right?!?! Anyways PLEASE help and ideas would be great!!!
How would i find out if it had an imobiliser?