I did a 90-watt, not a 150, but I'm pretty sure the wiring is the same. With mine, it came with a harness that plugged into the power supply and had 3 dangling wires coming off of it.
Red - Car battery, 8gauge I think.
Black - Ground. Some people swear by grounding to the frame, other to the battery. I did mine all the way to the battery. Again, I think it was 8gauge.
Yellow - Accessory. You basically need to find another accessory wire in your car (they're all over the place), and splice into it. It doesn't carry a heavy load really, it just has a signal thats on or off indicating whether or not the car is in the ACC position. There are ACC wires running into just about all the electronics in your dash that turn on/off when you turn the key to ACC. Find some wiring diagrams for your car or your stereo and you should be able to find the ACC wire.
Hope that at least gets you started