This article explains how to install KDE on openSUSE in case you had initially installed a different desktop environment, or no desktop environment at all, and decided that you want to try KDE or maybe even switch to KDE completely.
To install KDE you simply need to install the required patterns.
zypper install -t pattern kde kde_plasma
Logging into KDE
After KDE is installed, you can log into it by simply logging out and selecting KDE under Session Type at the login manager.
Switching to KDM
If you're switching to KDE you may want to switch to the KDE login manager (or display manager) KDM too.
Edit the file /etc/sysconfig/displaymanager and set DISPLAYMANAGER="kdm"
Or use YaST /etc/sysconfig/ Editor, and select KDM under Desktop -> Display manager -> DISPLAYMANAGER