It's also a good idea to check for polarity. Take your meter, turn it on, then to the voltage position, make sure it is set for DC, then touch the black probe to ground, red probe to either the white or black wire and with the lights on you will find the hot wire. Make sure you connect the camera properly or you may destroy the camera by connecting it backwards.
I added a second wireless camera so I could point it at a different angle and see farther down the road. My 12 volt supply came from a 12 volt supply already on the roof.
2013 Georgetown XL 378
2008 Honda CR-V