Netscape 3.*:

From the Listening Post main page, click on the hypertext link of a server name. The Netscape news reader will open and a connection to the server will be made. Once the connection is established, use "Add Newsgroup" under "File" at the top menu. Don't forget to subscribe to alt.toys.gi-joe by clicking the little dot just to the right of the newsgroup name. A check mark will appear.
 Repeat the process for each of the other listed servers.

Fort'e Agent/Free Agent:

Fort'e has a FAQ that includes instructions for using multiple news servers.
 

Microsoft Outlook Express:

Coming soon ...