I am new to the cnc mill machine.I know little knowledge about the cnc mill but not deeply.First i have to know about the setting the workpiece coordinate system, how to select a workpiece coordinate system,how to change workpiece coordinate system.

try taking a cam class at your local community college that helps alot.
you will need to know how to use the cam systems to do cnc it will make life a hole lot easier.
good luck.