When your schematic arrives, you will see which cavity of the round plug feeds which terminal on the circuit board. If it were me, I would get a trusted test light and attach the alligator clip to a good known ground. With schematic info, you will be able to figure out which cavity in the round plug should have power and which should not as the controls are activated.
For example, with the key off, pull the headlight switch and the terminal that powers the dash lights should show power.....and dim as the switch is turned. Hit the high beam, and the the terminal that supplies the blue high beam indicator in the dash should show power. Probe the others as well to confirm "no power" where there shouldn't be any.
Continue to confirm all cavities function as they should.
This is where I would start......But I don't claim to be an expert.
Best of luck
