I have been following these instructions (from the same site).
Installation
1.Download and install sabnzbd-version.spk to your Synology NAS.
2.Create a new share named downloads, give full access (read/write) to the user sabnzbd and to yourself to access the content.
3.To access SABnzbd web interface, go through the Synology Disk Station manager, the new icon in the DSM menu (might need a refresh), or directly through it address: http://yournas:8080/.
4.Upon the first start, you will be guided through the SABnzbd setup wizard.
5.SABnzbd will create the folders /volume1/downloads/complete and /volume1/downloads/incomplete. The first one is for finished downloads. It shall be accessible from the network by every one who can access the fore mentioned share. The second folder won’t be accessible to anyone. It contains parts of the assets currently being downloaded. As long as every thing is fine, you don’t need to go in there.
It simply don't work
PS: Synology DS410j with the latest FW .1742
