if you have the rpm, simply navigate to the directory where you've saved it , then open a console by pressing F4. In the console, type "su" to become root. It will promt you for your root password. After typing in the password, type "rpm -Uvh linux-source*.rpm", minus the quotes. This should install the RPM for you into the proper directory. If will give you an error message if there are any dependency issues..
Or, in Konqueror, you can simply click on the RPM and YAST should install it for you automagically
Hope this helps.