No sure if you have already done this or not, but I installed mine from the fuse box. Its really easy and I\'ve never mucked around with car wiring before. Once you work out with a test light what fuses your going tap (contant12v, ACC12v, dimmer etc) write down the amp number you need and head down to Jaycar and buy their fuses taps.
Makes things super easy and a tidy install. Heres the link below
http://www.jaycar.co.nz/productView.asp?ID=SF5120&keywords=fuse+tap&form=KEYWORD
cheers