F-150 wont turn over

Truck is parked, after girlfriend drover it alone, and returned it, the next time i
went to use it, wont start.
When I turn the key, st position all dash lights stereo turns on same in 2 key
position, but with the final and 3rd position that would crank the engine and
start the truck, it dooesnt stgart and everything thaat was on shuts off.