Truck Starter isn't triggering the motor.

Now I just recently replaced my whole engine in my truck.  (Ford F-150 1995 XLT)
It started when I tried to head to work yesterday.  I turned the ignition and the starter wouldn't stop trying to turn the car on.  Even when I turned the key to turn of my truck, The starter kept trying to catch the motor.  When it stop I decided to let it sit over night.  I come back and now my battery is dead.  Now I jump starting it and the light keeps flickering in a rhythmic pattern, but the truck still refuses to turn on.  My uncle and I think it's something about a regulator.  But we aren't sure.  (I myself don't know much about fixing cars.  and My uncle doesn't know much about Ford engines, so we're really in need of some assistance.)  It was working fine yesterday.  Once I parked it, and came back it decided to die on me.