Trying to find compass heading from magnetometer

I follow you to a point, but I don't know what you mean in this bit

Point the X axis North and take a reading, then point it South and take a reading. Do the same for the Y axis.

Do I have the puck flat on a level surface and align it to North and South do the X axis (like turning a knob), then do I tip it on it's side and turn it (like a spinning coin) to do the same for Y?