i'm assuming you actually have kde 3.2 running.
go to "configure your desktop", "look and feel"
there you can pick what aspect of the theme you want. there is usually an option to install new... just browse to the file you downloaded, and if it's compatible, new eyecandy.
from what i remember, there might not be an option for a complete theme, just peice by peice.
you could try and make a directory : /home/you/.kde/share/themes , and unpack the file there. that worked in 3.1, so it can't hurt to try.