Drop it in the folder with the other ArtCam post-processor files (I think its named PostP), restart Artcam, and the new options should then be selectable - when you go to save your next toolpath it should be on the list. I believe there are actually two post processors for Mach - inch and metric.
How the g-code functions then with your controller and hardware setup, who can say, but that is how to get the processor installed and the g-code generated.
I use Mach3 myself, but do not use the Mach post-processor - Mach nicely eats one of my other machines formats as well, and so I only use one format for portabilities sake between them.
How does a postprocessor work in artcam? There is a post processor in artcam for .NC, but how do i use this.
Just look in the postp files how they are build up.. It's plain text..
I wrote several postprocessors for ArtCam for different machines and interfacing programs like WinNC, EaziCNc.
You only have to know what your CNC talks..