Neutral goes to screw 5 . Live goes to screw 4 which is then connected to screw 1. When the relay activates, screw 2 then becomes live and feeds power to the fridge to get it to do whatever you need it to do by setting the temp. controller to heat or cool. I sought the advice of a professional and a hefty relay is interposed between the controller and the fridge because of current surge when compressor cuts in. However, the controller can be used on a heatbelt without any fancy additions.
You may find this more helpful. Dated 7/16/12 from bistr http://www.homebrewtalk.com/f51/help-needed-337318/
best of luck.