The unit has a relay that is opened and closed by the house thermostat. There should be a small brown covered wire... These go to the 'primary' side of the relay (the part that carries current through the relay coil).

One side of the secondary part of the relay (the part with the heavy contacts) are internally connected to the compressor and fan circuit. The other side, the one with the terminal screws, is for connection to the power lines. In a 220V circuit, it makes no difference which of the two wires you connect to which terminal.

The bare wire coming from your house wiring is to ground the unit (Usually a green screw). Hope this helps.