If a 1992 F150 six cylinder was fine then wouldn't start but the battery is OK is this most likely the solenoid where is it and how do you test it?
The solenoid will be over by the battery, attached to the radiator support. But, it could be a bad ignition switch, bad battery connections, bad ground, or even the wire at the starter could be loose. You will need either a voltmeter (DMM/AVMM)or a test light. It would be good to have a friend help you out with this.