You need to add below repository to your system and install using zypper as following, as root :
zypper ar http://download.opensuse.org/repositories/home:/frispete:/RemoteDesktop/openSUSE_11.1/home:frispete:RemoteDesktop.repo
zypper in NX
zypper in FreeNX
Also find this quick user guide in pdf format : FreeNX Quick User Guide
PS. The user guide was obtained from http://mail.kde.org/pipermail/freenx-knx/2008-May/007059.html
Tags: openSuSE 11.1, remote desktop