After some playing around (and someone else finding the root password on the unit), the easiest way to enable ssh is:

1. Boot the NAS up.  We assume you've stepped through the standard setup process via the NAS Web page and have set the admin password.
2. Navigate to http://nas_ip_address/support.html and enable remote ssh access.
3. SSH to the device and login as root with a password of 'soho<admin_password>'.  Eg if the admin password was 'pAssword', the root password for the NAS would be 'sohopAssword'.