In ~/tmc/configs/tormach_mill, edit tormach_mill_base.ini
In each [AXIS_0 or1 or 2:
MAXLIMIT is your max travel in inches. Depending on which end you want the limit to home to, add a minus in front of the number.
In my case I home so the the spindle is over the left rear of the bed. AXIS_0 (X) has a positive number (the home/limit switch is on the left). AXIS_1 (Y) homes to front (spindle at rear). This means using MIN_LIMIT with a minus in front.
This file gets over written when you upgrade so you will have to edit the same parameters in the newer version.