look at your fuses your in box for the brand name of the circuit breaker.... head to the homedepot and get a 40 amp 2 pole...
Does your power supply box have 3 or 4 wires (red black green white)
Wiring a powerbox to your fuse box is very easy to do
red black to the 40 amp circuit breaker.....
normally on newer installed fuse boxes all the white wires will be on one side of your fuse box left or right on a bus bar and all ground(bare or green) will be on the other side
this helped me a year ago
[video=youtube;OlGIHmqacgU]http://www.youtube.com/watch?v=OlGIHmqacgU[/video]
http://www.youtube.com/watch?v=hDnHz0bRAKw