Here's a wiring diagram for the MH1210. You can wire a male plug on the input (line) side and a female socket or a wall outlet on the output (load) side.
Black is AC Hot, White is AC Neutral, Green is Safety Ground (and like all of these controllers, there's no provision for a Safety Ground on the chassis)...
Cheers!
[edit]
I tried your wiring method, day_trippr but it didnt' work (no power to the unit).
That wasn't my wiring method, I was just correcting someone else's because it clearly wasn't going to work. He made that change and it worked.
If you followed that image and your controller isn't lighting up, I bet you have the line power coming on the load side - which doesn't connect to the controller's power supply (it's on the wrong side of the relay). Follow my drawing below and it'll just plain work.
If you wanted to hardwire the relay to control a compressor, you just need to open the circuit at the compressor and wire the load side hot lead to the compressor input, connect the neutral to the fridge/freezer neutral circuit pretty much anywhere, then tap into the line side hot wire inside the fridge or freezer for the line side hot feed. No need for plugs or sockets, you just need a spot to stick the controller...