Using a Multimeter (Noob)

Hi, I am fixing my mate's Marshall Footswitch, it was cutting in out on one channel so I cut it back and re-soldered the wires. So now I am up to testing it.

I just bought a Multimeter (it is nothing special) and I was wondering how to test the switch? When we first tested it, I saw my mate test the single cord coming from the footswitch... But I don't understand this if all the diagrams involving Multimeters use both testing cords.

Here is a pic of the switch.
https://en.woodbrass.com/images/woodbrass/PEDL009.JPG (Close enough).

So I'm testing the cord, correct? What measurement should I have the Multimeter on, and what cord do I use (red or black)?

Thanks, Mark

Try this link. I think you care about continuity and resistance sections.
Multimeter Tutorial