[UbuntuGnome] Plex movie files on Ub 14.04

Has anyone experience of setting up plex on a Lan? I am using the Roku (Now TV) as the receiver of the videos, but having reinstalled Ubuntu I can not set up the plex server to see any of the files I wish to stream.

I have tried:

Going to the external HD where the files are located and creating a link into the home directory.
Changing the permissions on the link and the Ext HD drive to 777 (I don't think the drive ownership changed). The link in the home director to the ext HD can not be seen in plex as an entry in the home directory.

Pointing plex to the actual directory within the Ext HD drive. The HD can be seen, but not the directory with the files for streaming.

Has anyone got round this problem?