mt plugin installation

OK, I've done a fair bit of searching round MuNuviana and the like, but I can't find anything on how to install a plugin on MuNu. My designer wants to install a small plugin for my new skin that shows the 'top commenters' on my site. She would usually install it "into the plugin dir. in the dir where mt.cgi file is, and obviously on mu nu it isnt set up that way."

Any ideas on where she should install it folks? Or aren't I sposed to be installing plugins? Thanks :)