they are a piece of piss really, you can take any supply, from the sig lighter, the battery, evan the wires which i have done is add mine to my amp power and earth and just extended the wire down the car, it's really easy, i evan put one in my grill last night and i think it looks quite good, chavvy but yes i like it so care.
they are honestly the worlds easiest job to do in my opinion, all you do it just the longer the wire you want the longer to you make it, the place you want them you put them it's really easy, and the switch can be placed anywhere as long as the wire is extended. i have about a meter of wire now used to run these things all around my car, i just used the cheapest of speaker wire to extend everything, here's a pic of it in the grill.