I am not an electrician but this is how I did it. In my camper, the white wire is the ground and the black is the positive wire and the running lights are connected to the blue wire. I found that connecting the two connectors with the insulation pushed back so I could see the wire colors was much easier than trying to reverse the feed plug positions in my head. Use the notch in the plug as your guide to aligning them. Be sure to install an inline fuse prior to connecting to the camper. Remove the fuse prior to doing the wiring. When I camp for extended periods I use a separate 12v battery which I install just forward of the wheel well and use the same type of connector to wire it to the camper.
I hope this helps. In truth, all this "lektical stuff" is magic.
Mike