This is how I set mine up. So far it has worked great. This is just one of many ways it could be done.

I used a channel iron for a base and welded it to the uprights at the front of the deck. I also bolted the fairlead to the smaller channels that were already on the neck. I imagine some trailers are designed differently, but they were there and too convenient to  not take advantage of. I have a large battery in a plastic box secured in the neck and used the same cable that my power tarp roller on the grain trailer used to make connections. I found plugs and sockets to match the power tarp system, so that I can use the semi tractor when needed to pull the trailer, and installed a set of heavy cables on my towing pickup from the batteries to a receptacle mounted in the bed. The up side to that I found later, is I have my slip in fuel tank wired with the same plug. Very convenient-and it looks like I actually had a plan! The battery plus the heavy cables are probably overkill, but I have never had a low power problem. I found a cheap wireless remote on ebay for the winch so I can guide my treasure onto the trailer while operating the winch.