Go to nVidia's site and download the nVidia installer. You select the right one the same way you do for Windows drivers. If you're running 64bit Linux, you will need t select "Linux x64". If not, just select "Linux". Once you have the file, you need to exit from KDE/Gnome/whatever and get to a normal login (alt+n at the login screen). Login as root, move the installer to the root directory, and run it. Normally you run it by using "sh ./NVIDIA-Linux-blahblahblah.pkg". Note that you need your Linux headers and building tools installed to do this. Once it builds and installs, reboot and enjoy.
