Security reset

MY car is a 94 Olds Cutlass Supreme, 6 cylinder, 99986 miles on it,

Car was great when I bought it 4 months ago, never a problem until last week, battery went dead, jumped everything was fine, then it would not hold a charge, so last night I bought a new battery and put it in while still in the parking lot, all we did was install the battery and now the car just wont start. Battery was tested and is good, the red security warning is now flashing and everything (Radio dashlights everything) is good, engine just wont even try to turn over. Someone told me that the computer locked itself, called roadside, they told me same thing, told me to put the key in the accesory position wait 5 minutes then turn over, the compute should reset. I did all this and the security light is still flashing. What can I do, I dont want to spend 200 dollars to fix what a 50 battery change was suppose to be