Step by step guide for idiots ( idiot, me )
Right on..!I'm not an electrical person, but we could talk a little, get you calmed down and establish what you do and don't have. We talked about your clutch a couple of weeks ago.
OK, now if you can post the model or photo of your meter, we can give you a few hints, there. Or if you have a test lamp, that may be good enough, meter tho is better.
START VOLTAGE
Bear in mind there is only so much going in/ coming out of the key switch:
main power into the ignition switch, hot all the time, unless fuse link is blown
RUN: In the run position, ACC (accessory) and the "run" or IGN1 line is hot. This branches off, feeds the warning lamps and gauges and comes out through the bulkhead connector, usually dark blue, and feeds (depending on year/ model) the siwtch side of the ballast, the blue wire on the connector for the VR, and the light blue going to one of the two field connections on the alternator. Electric choke if used, and a couple other things if equipped
BYPASS: When the key is twisted to start, BOTH the ACC and "run" lines GO DEAD. The ignition power during starting comes from the IGN2 terminal on the key, often brown, comes out through the bulkhead connector, and terminates at the coil + side of the ballast
START: Meanwhile, a separate contact in the switch also is "hot" during crank, this is often yellow, comes out and connects to one of the small flag "push on" terminals on the start relay. This is the "start" signal, which would turn on the electromagnet (coil) in the start relay HOWEVER the SECOND flag / push on terminal MUST BE grounded. If you have an auto, that second terminal goes down the firewall, over the top of the transmission, and connects to the center terminal of the reverse/ neutral start switch on the Torqueflite. If you have a stick that goes through the firewall (single grommet) and connects to the clutch safety switch. When the start relay energizes, it feeds power and energizes the starter solenoid, cranking the engine
If nothing at all works in ACC or "run" you are likely not getting power through into the interior. DO THE headlights work?
Go out to the engine bay and probe the large black connected to the output stud of the alternator. This should be 12V at all times. If not, you have a blown fuse link, bad connections in the bulkhead connector or other problems
FUSE LINK: This is a special looking wire, with a molded tag attached. it usually goes from the big stud on the start relay ( battery power) to the big red wire going through the bulkhead connector. Probe and test those, should be 12V at all times. If not, go back to the starter relay "big stud." If that is dead, you likely have main battery cable issues