The names.nsf is a local file which needs to be "synched" the first time a user is enabled on the BES via the "Synchronize Address Book" menu option. Once that's done then the following procedure an be used:
Select a user and choose the "Edit Properties" option. Scroll down to and select the PIM Sync option on the left-hand side. In the view on the right-hand side, scroll down to the Address Book description. Find the following - "Location -Server" and "Location-Relative Path". Place the heirarchical name (servername/organization) and the path (mail\username.nsf) to the users' mail file in the described areas.
The above allows the Wireless Sync feature to be active ithin the Address book view.