I have not found a switch or a reset button. Any ideas where I might look for this "brain box"?

My 1993 Ranger won't start. I believe it is the security system but I don't know how to disarm it reset it, or disconnect it.. There is a small red light on the dash left of the steering column. The light is off when I'm driving and on when the truck is parked. Over the last couple of years...