Hi,
I mounted two microswitches, one on the end of the X axis rail, set so that when the laser mount moves fully to the left it closes the switch, the other on the left front (nearest to the side with the control circuit) set so that when the X axis rail moves to the front it closes that switch.
Both switches are connected in parallel, (common pins together and normally open pins together) then one set of contacts is soldered to pin D9 on the arduino the other to the ground connection. Set T2 Laser, control laser, settings, select "Home Switches" and that's it. (I fixed the switches in place with very strong double sided tape, works well but would probably be better to use nuts and bolts!)