How to put a switch on a power supply?

[mamba max1]

I have a server PS that I'd like to put an on/off switch on. Obviously, I have no idea of how to do this. The PS is rated for 42 amps and 540 watts. Excuse my near complete lack of know how regarding circuitry. Despite that, soldering is not an issue for me...even with very small things.

#1) what rating of switch do I need? (if it makes a difference I live in the US)

#2) where/how to I solder it up?

If I need to post pics, let me know.

Thanks!