What exactly happens when you turn the key to START? Does the radio shut off? Do you hear the starter relay near the battery click? If the radio doesn't turn off, the problem is inside the column, between the lock cylinder (where the key goes) and the ignition switch (underneath, with all the wires). If the radio stops but the relay doesn't click, the problem is in the starter interlock. What transmission does the truck have? If you don't know the exact model, read this whole caption & add your truck's details to a signature so they show with every post:
You can omit "F150" and "19.." since we assume that. But put the 2-digit year, engine size, transmission model, trim level, cab/bed configuration & wheelbase, transfer case model (if 4WD), gear ratio, tire size, miles (or KMs), mods, maintenance, damage, repairs, etc.
If there are any terms you don't understand, read this: Automotive Terms & Abbreviations
Uploading pics of your truck would also help. This forum supports pics, but it's easier to embed them in your posts if you follow the instructions at this link: