I wrote this a while ago so it may have change a little bit – I hope it helps.
<b>Information taken from the following IBM Technote</b>
<b>Option 1: Automatic</b>
Administrators can configure a Sametime server to force updates to all of the Sametime Connect clients within the environment.
Summary of steps:
1. Using a Notes® client, open the stconfig.nsf file (located on the Sametime 7.5.x or 8.0 server) and double-click the ‘CommunityClient’ document.
2. Edit the “URL for UIM Provisioning” field by adding the full path to the update site. Make sure you include http:// in the link. The field does not automatically add it.
URL for UIM Provisioning: http:///STclientupdate/site.xml
3. Beginning in Sametime 7.5.1, you are also required to put this URL in the “Sametime update site URL” field in the Policy which applies to the users. You can edit the Policy by going to Administer the Server via stcenter.nsf on the web.
4. Save the changes.
5. Restart the server.
Now, when users log in, they will be notified that their client has received updates.
<b>Option 2: Automatic</b>
Update the preferences.ini file located on a user’s workstation with the URL to the update site. The preferences.ini is located in this directory:
\Program Files\ibm\Sametime Connect\plugins\com.ibm.collaboration.realtime.update_1.0.0
The format for preferences.ini is:
<b>Option 3: Automatic</b>
Domino® 8 servers introduced a new option for deploying Eclipse update sites, which can be used with Sametime clients: the Eclipse Update Site database.
For information on exactly how to deploy this database on a Domino 8 server, reference the Domino 8 Administration Guide or Information Center topic: Understanding the Eclipse update site
* Note that this functionality does not work with a default Sametime 7.5.x Connect client. Contact IBM Support for a hotfix which can be applied to these versions if you are interested in using this method as a Sametime update site.