Yast is garbage. The best way to install rpms is:
1) Using konqueror navigate to the folder where there are the rpms.
2) Go to the Tools menu and click Open Terminal (Note that this may not work if you use KDE 3.4.x and you navigate through the media:/ protocol. Either use the file:/ protocol or upgrade to kde 3.5.3)
3) In the terminal that appears, write:
sudo rpm -Uvh package1.rpm package2.rpm ...
where package1.rpm and package2.rpm are the rpms you want to install. If you want to install all the rpms in a directory, do:
sudo rpm -Uvh *.rpm
Note that rpm does not resolve dependencies so you have to do this job manually.