starter relay

OK, the "big stud" is two functions--junction point and one contact of the relay. It goes main cable from battery --to stud-- main cable to starter

The "square" goes to your starter solenoid (small stud on the starter) with no 12 or 10 wire

One of (doesn't matter) the bottom "push on" terminals, marked IGN and GROUND in the diagram, goes to ground VIA your neutral safety switch on the transmission, or the clutch safety switch if used. If you have a stick/ no clutch safety, just ground it

The remaining "push on" (yellow in the diagram) goes through the bulkhead to the start terminal of your ignition switch. As I mentioned, if you have the seat belt interlock under the hood, this is in series.

Mopar uses these for two reasons---it relieves current on the ign switch, because the solenoid draws a fair amount of current, and the wiring of the relay allows the neutral safety circuit to be a simple one wire "grounding" circuit.

Your auto trans should have three terminals on the NSS. The two outer terminals go to the backup lamp circuit, and the CENTER terminal goes up to the starter relay

What are you doing for a harness? If you are using a factory harness, it should all hook up. If you have some sort of aftermarket, you may have to add some wire.