how do i go about installing separate+ in linux

hi,

i'm an ignoramus on the ITC-side of graphics, but i've been looking for a way to get the separate+ plugin into gimp, so i can convert images in RGB to CMYK.
Don't get me wrong, i've been looking around and reading, and i did download the latest version form:

http://cue.yellowmagic.info/softwares/separate.html

but it just doesn't seem to work. Where exactly do i copy it to for it to show in the image menu of gimp?

reason being i'm getting different colours when i export my files in scribus to PDF and get them printed digitally. I want my pictures in scribus to be CMYK.

thx.