Depending on the distro you use, there will be some style package updates in your repository that match the kde version you use. Search for them, install and enjoy
If your theme isn't included anymore, have a surf at kde-look.org - chances are you'll find a package for your distro from the maintainers of the theme. If not, you can compile it from the sources, therefore you need the gcc-compiler and kde-header packages installed on your computer. For other dependencies and how to compile it, check out the maintainers documentation.