You need to buy a special harness which is about £30. This runs from your battery on the car and has a quick connect plug that ends in the boot. You simply hang the winch on the towbar, open the boot and connect the cables.
You then take it out of gear and pull the steel cable of the winch and connect it to your trailer. There is a remote control that has about 3m of cable. You simply put it in gear ( the winch that is ), select forward or reverse and push the button.
It is effortless. I have pulled my trailer/boat out of sand where I cannot even see the wheels, up steep slipways and out of mud. The winch I have is capable of pulling nearly 4 times the combines weight of the boat, trailer and engine.
I always chock the back wheels of the car and put the handbrake on.
Have a look on www.trailerpartswarehouse.co.uk
, they have a variety of winches for all sorts of needs and at varying prices. You can also buy the towbar adapter and additional wiring harness from there. Mine was just over £300 with everything but it has been well worth it.