First, your need to find a near and fast mirror (fast is more important, but less pc).
http://www.suse.com/us/private/downl...t_mirrors.html
Next, open Yast -> Software -> 'Change Source of Installation'
click 'Add' -> 'HTTP' (or FTP)
enter server name and path to the desired version, e.g.:
Server name: suse.osuosl.org
Directory: suse/i386/9.1
Authentification: anonymous
click 'OK'
You may need to inactivate the CD source or set it to lower priority.
Now you can install software the usual way using Yast.