To get started, connect the V+, V- and ground pins to a regulated bipolar +/-12V supply. You don't need much current, it's only rated to draw 15A.
Now put an oscilloscope on the output pin, relative to ground, measure what waveform you're getting out. Now run a mains line through the Hall effect sensor, turn it on with a good load current, and measure what comes out of the sensor. Once you know what the actual output looks like you can design appropriate signal processing going into the Arduino.
Remember you need only one of the mains conductors passing through the sensor, if you have, say, a cable with active and neutral together then the net current through the sensor is zero and you won't read anything.