Hmmm... You won't get a lot of responses with absolutely broad titles such as "Linux Help", and saying you've installed "Linux 9".
Let's get past the first problems here and hopefully you'll be able to pose a better question for folks to answer...
The title of your post should reflect the problem yuoa re having, otherwise not many people are going to waste their time reading it. So, I would suggest something more along the lines of "Installing Themes under *** on *** v ###"
Now let's get to the second part of the problem with this post... You said you are running "Linux 9". There is no such thing unless a new distribution has suddenly come out grandly calling itself "Linux" and startig its versioning with number 9.
My point is, nobody know what you are talking about. Beofre you get frustrated with this response, recognize that I'm not trying to be an ass or make you feel bad. I'm trying to help you.
There are a ton of distributions out there, all based on Linux. Linux is the kernel (just a piece), not the whole system you have installed. I am running Fedora Core 4 on this system, for example. Further, I am currently using the Gnome desktop (a windowed environment based on X11). But everyone who uses Fedora Core 4 is familiar with what I am referring to without me getting into much further detail...
So it would have been a much better title to write something along the lines of: "Installing Themes on Gnome under FC4". Then ask your questoin in the post. This would give people plenty of information to form a proper response.
As things stand, I know you're running version 9 of something, but I know not what. RedHat9? Yellow Dog? SuSE9? Mandrake9? Bob's S00p3rd0093R #@X0r $ys^3m v9? And further, I have no idea which desktop you are using, and this would definitely be important if you are wanting to install themes. Gnome? Xfce (does this one even have themes, I wonder...)? KDE? ThEGnOMeSysTeMThaTIcomPiledMySElfAndTRiEDtOConVINCeEVRyonEIwroTEITmYsELF v0.1?
Anyway, I hope you understand what I'm getting at. Give more information in your message title to clue different readers with different areas of expertise a heads-up so they can choose to read your message or not, and within the message give everyone as much information about the system you are running and particularly which parts of it you want to change before posting it.
Now revamp your question, and try again. Then someone will certainly give you a hand!