Ford F-150 clicking

make sure that your battery cables are clean and tight. also check the starter make sure all wires are clean and tight. then try tapping the starter with a hammer while someone turns the ignition key if it starts you need a starter

Check battery voltage, it should be minimum 12.4. Check the battery cables for corrosion and make sure they're tight. If cables are ok, check voltage signal at the starter relay that's mounted on firewall by battery as you try to start it, if there's voltage at starter relay "S" terminal replace starter. If no voltage present trace back to the safety neutral switch but it's now called transmission range sensor