I found the solution to my question. Solder a line of header pins into the hole in the gshield above D9 through GND. Twist together the leads from your N/O X-axis limit switches and solder them to a pin in D9. Repeat for y-axis switches and solder them to pin in D10. Repeat for Z-axis switches and solder to pin in D11. wire common to GND.
In future gshield upgrades, Synthetos should consider adding jumper pins or a socket for these pins, as soldering to the very tiny solder pads on this board is difficult. Also, if use of the micro stepping feature requires two jumpers, thye should provide two…I only got one.
