Hey there,
Do you have a factory radio in your car or an aftermarket radio in your car?
Your monitor can be powered either by the Wall (ac) or Car (dc).
You stated your don't have the cig plug. Is that the cig plug that usually comes with the screen?
You could go to radio shack and buy a Universal DC adaptor
http://www.radioshack.com/family/ind...032056.2818117
I 'll assume the unit is powered by DC. Yellow/red is your power(+) and black your ground(-). You can ground it to the car or you can attach the ground to an exsisting ground. Youll splice into the red/yellow for power and black to ground.
Hope this help