Hi, Scott
You can also use Active Tool Offset's
Not an expert hear, Go to Offset's page, click on Fixture 2 G55, enter your table offset's ( value you want is the location you want to start cutting on table).
Now return to Program Run Screen Regen tool path, you should see your item to cut is offset by the amount set in Fixture 2 G55.
In the DRO's you'll see a -X, -Y value, that's shows current position of where your located from fixture offset, if you click on Machine Coord's you'll see ABS X 0, Y 0 which is your Home Ref. point.
Now you can Run your Gcode should be fine.
Changing back to Fixture 1 G54, Regen tool Path will return your Cut and View Ref. to Home location
Just scratched the surface of offset's, many other ways to do this like, editing your Gcode, insert a G55 just before your first cut, save changes, ref Mach3 manual in Tutorials above .
Dry Run this to confirm propper operation.
Don't Forget to save the Fixture offset's on exit of Mach3.
Hope this Helps ,Chip