Still trying to grasp this whole linux thing.

I want to install the Dark Plastik theme from kde-look.org
This is what the install tells me to do...
How can I find out where Kde is installed too?
When I do a locate KDE, it shows me so much stuff I have no idea where it is..
Also. What is this --prefix=PREFIX thing... Does it mean I replace both prefix and PREFIX with the location?

Peeze help!

Basic Installation (from the console):
- Step 1
$ ./configure --prefix=PREFIX
- Step 2
$ make
- Step 3 (as root)
# make install

where PREFIX is the path to your kde
installation eg: /usr, /opt/kde

Ok I think I've got it installed. I used /usr/lib for the PREFIX and it did a bunch of stuff then ran through rest of steps. How am I suppose to turn this theme on now? I went into theme manager and and Styles and a few other things in the KDE menu but i didn't see anything to do with plastik....