No headlights on '75 duster

Hi, thanks for the reply. I have the chilton's manual and these diagrams:
http://www.mymopar.com/downloads/1975/75ValiantA.jpg
http://www.mymopar.com/downloads/1975/75ValiantB.jpg
But not too sure what to look for there.
Here's what i did today, i plugged the red (+) wire of my voltmeter to the + terminal of the battery, and the negative into the headlight plug which showed my 12 volts on 2 of the wires. I guess high and low beam. So that means that the ground is ok right?
This was with the headlight switch off.

I am not sure how to test the headlight switch terminals, because to turn it on the switch needs to be plugged in, and then i cant stick the voltmeter probes into it.. I hope i am making sense lol.