To enable SSH you need to goto support.html, i.e.
http://nas.local/support.html, or replace nas with the IP address of the nas.
A support screen with come up, and you will need to click the enable support features, then click SSH access, and click apply.
Now the ssh server is running on your NAS you can login to test it, e.g. ssh
[email protected].
Your password will either be soho, or soho + your admin password (if you have set one.. and you should!), ie. sohoMyPassword.
If that all worked well logout of the nas and you can setup a backup script with rsync over ssh, e.g. rsync -avze ssh
[email protected]:/nfs/shares/ ~/backup