Low Beams & Tails Lights don't work

[TokenWhyteGuy]

I went through a flood and my low beams and tail lights went out.I tried changing out the switch on the steering wheel but and it worked then I turned my car on and it stopped and would'nt work again.I believe its the wires and I went out and got a Multi Meter but I have no idea how to test which one is bad and how to replace it if its the problem or if theres something else I don't know about thats causing it.

Please help anyone, I need detailed help not just hey check this or check that, I'm new to working on my own car.

Thanks.