at the bottom of the column, in the area of the brake pedal is the ignition switch.
make sure the truck is in park or neutral with the parking brake set.
remove the switch from the column. it should be 2 bolts with 7/16 wrench heads
with the switch out, use a small screwdriver and see if you can start the truck. if it starts, the switch is either miss-aligned, or the ignition actuator is broken.
if it does not start, either the switch is bad, or the wire is not connected to the solenoid