I had no idea about this when I started to use Plasmac either. But if you move the torch above the X,Y zero point where you want to start and touch off the X=? to 0.00 and do the same thing on Y=? you are good to go.
I might add that you may need to touch off the Z axis once when setting up your machine. My machine has 86mm of travel so I jogged to top of travel and touched off Z to 86.00 mm (eg. Press Z=? and set it to 86.00) I have never had to revisit this Z axis setting.
