Before you can set your tools in the machine you have to know how the program is figuring out where the part is located and take it from there. Your part needs an origin point usually one of the corners if it is a rectangle or square. If the program is designed to cut from the top surface down then all you have to do it touch off on the top of your part and set your Z for that tool there. If you are using cutter compensation (D#) then you have to measure the tool and input the proper information in the offset page for that tool. All machines are different in how they measure tools and derive offsets. Some programs require a "Guage Length" established by the programmer in that case you will need a Tool Presetter and either add or subtract from the guage length and this is your off set. It could be plus or minus. You would be far better off to ask your supervisor how your particular tools are set for any one machine so you will know for sure how to do it. And avoid a crash.