Take a look at this thread, it might be of some help:
I've never been able to add just any directory to the software mangler, it's always had to include a proper hdlist.cz file
On the upside though, it simple enough to install rpms and use the software mangler database(for auto-dependencies and such). At a terminal, try urpmi <rpm name>. That will attempt to install the rpm and satisfy any dependencies that exist in the database.