Let me give you the flow of things. There could be a problem with the factory alarm. So do this first...
Use the key to unlock the doors from the passenger's side. Check to see if the engine will crank. If not: >>
1. Verify that the battery is good and is charged - done
2. Verify that both battery terminals are clean - ?
3. If you turn the key on, verify that the instrument panel warning lights that usually come on are on - just verify that there is power lighting some things up. - ?
4. Turn the headlight switch on and see if the headlights light up. - ?
5. Try to start the engine while the headlights are on and even though the engine starter may not operate at all, note whether the headlights stay on or dim out while in the cranking position with the key. - ?
6. If they stay on - go to step 7 - if they dim out recheck the battery connections ?
7. Get access to the starter with a 12 volt test lamp, attach the clamp to a good ground. - ?
8. Use the point of the test light and touch the large diameter wire on the starter stud and verify that it lights - ?
9. Now, with a helper in the truck, touch the pointer to the small wire stud and tell the helper to turn the key to start the engine. Verify that the test lamp lights up. This is the signal from the ignition switch to operate the starter. If it lights and no starter operation, you have a bad starter. - ?
10. If the test light does not light up then there is a problem with something before the starter like neutral safety switch / park-neutral switch or ignition switch or wiring.