I am looking into putting together a cnc mill. I am trying to familarize myself with the whole process. I have used rhino3d and uploaded a demo file into visualmill and it recognizes it and displays the 3d image. How do you actually create the g-code in order to put it into mach software? do you save it as a particular file or does it create the g-code in text so you can copy and paste it?

http://www.mecsoft.com/Mec/Training/VisualMillresources.htm

Here is a link with some useful videos
For post you have to choose the mach controller you have at the post processor optionsa and the posted file extension to save it and load it after to mach software