This will have to be a rough guide because I am using neither SUSE nor KDE...
1. Find and click on YaST icon
2. Under Software, select software management
3. search for kde-desktop, additional required kde packages will be selected automagically
4. accept all changes
5. logout or reboot
6. when prompted to login, there is an 'icon' called sessions (probably).. change it from gnome to kde
7. login and (hopefully) voila!
cheers