How does one find and set up a Touch Off

Hello, So trying to find and set up a Touch Off, I can see the Touch off when using the Linuxcnc, but I want to set up a table 12 inch length and width, not sure how to also set it up so that the tip of the tools knows where the material starts.

Not totally sure what you are asking, but usually the machine will have home switches that set the machine origin. Then depending on where the workpiece is placed on the table, you will touch off the x and y for the workpiece origin. A simple way of doing this is very slowing jogging the cutter closer to the workpiece, while spinning the collet by hand. Once the cutter is just barely rubbing on the work, I will touch off and set that axis to 1/2 of the tool diameter (a negative value if touching off at the left or front). Repeat for the other 3 axes, except set the Z touchoff entry to 0 when the cutter touches the workpiece.

Hope that makes sense and answers your question.

Ah sorry, so currently I'm using linuxcnc as a simulation, since the homemade machine isn't ready, I'm playing around with gcode. But I need to later set it up so I don't accidentally drill a hole into the platform (touch pad?). I apologize for not being better at asking questions.

So to perhaps state it better, how to I set up the point of origins(x, y, z) on linuxcnc to a specific area as if there was a table there and I want one corner to be the origin. Also how to I adjust the z axis to account for the height of the material being used. (hope this is better)

Setting the origin ( home ) is easy and can be done in several ways, but usually in manual mode you jog to where you want the HOME of X Y Z to be and press the Home button in the GUI you are using or in automatic mode with Home switches installed you just press the Home All button and the machine moves till it finds the switches then backs off a bit and sets the 0 ( zero ) for all axis.
For finding the material in manual mode you jog the Z axis down till it touches the material and press Home so that zeroes it and you can run the gcode. In auto mode you do the same jogging but you press the Touch Off button and set the 0 there.
Or you can use a probe sensor and have everything done automatically at every tool change.

touch off is the PART Workcordinate system
while homing is the mashine
for touchoff
please see here how this workes