From Fedora Project Wiki
Step by step tutorial for installing KDE and removing Gnome:
- Open up Terminal .
- Log in as root via su .
- Enter yum install @kde-desktop system-switch-displaymanager kdm
- Now enter system-switch-displaymanager kdm
- Reboot your machine.
- Log in, and be sure to choose KDE as session.
- If you plan to remove GNOME, continue; otherwise you're done now.
- You can now enter yum remove @gnome-desktop . Watch out that this doesn't remove any programs you want to keep!
- Now you should be able to use KDE as the default Desktop Environment.
Thanks to shivam for contributing!