We currently do not have a tutorial on setting up the emergency e-stop button, however it works very similar to a limit switch. (limit switch tutorial: https://buildyourcnc.com/PrimeronHomingandLimitSwitches.aspx)
There is 2 sides to the e-stop, first being green NO-Normally Open and secondly being red NC-Normally Closed. From these two sides you will have too choose in which manner you would like to wired the e-stop.
If you plan on smashing the button when there is a problem, (as we all do :D) we would recommend wiring it in normally open - Green side. The wiring is simple, you will only need 2 wires going from GND to the input pin, the orientation of the wires is not as important with these switches.
You will go to config/ports&pins/inputsignals, there will be one item in that tab enable, e-stop, you will then enter the pin number and you are done.
Planet-CNC:(with our board) there is not designated pin which we would recommend wiring it directly to the power cord going to your CNC electronic power supply. Wire it in normally open and to the live/load wire.
3rd party board compatible with planet-cnc or a direct planet-cnc board, go to file/settings/general, there you will choose the output pin for your e-stop as stated on the board schematic.
"On a personal note: I have ran into 1 issue once being that they placed the colored covers on the opposite sides, which means that green is red, and red is green. I only ran into this once but I would rather share this info. as a possiblity."