This dialog serves two purposes. First you indicate an offset for loading the part onto the machine. Second you can select the machine simulation file that will be displayed during simulation.
The Xoffset, Yoffset and Zoffset parameters represent offsets for loading the part onto the machine. For simulating single milling or turning setups these offsets are applied to the setup after the part is aligned with the top most location. for indexed parts or turn/mill parts, the offset is relative to the stock axis.
If you purchased the machine design option, you can select the machine design model in this dialog box.
You can identify a specific file by selecting Always use this one and selecting the file. Remember that the number of turrets and locations of the turrets must match the selected post processor. You can also select Use the one specified in the .cnc file to use the machine specified in the post processor .cnc file.