You can wire them to whatever, there's not a certain wire they have to be connected to, but most people wire them to their parking lights. which are brown (12VDC) and black (GND).
I've been wondering about these headlights, if they're the new ones off eBay with the LED strip for front parking lights. It's a simulated CCFL, right? Just an LED lighting up a plastic ring? Also, how's the light dispersal and beam pattern on them? Any chance you could post up some pics of the lights themselves and a pic or two of the highs and lows shining on a wall?