From MozillaZine Knowledge Base
To join a newsgroup:
- In Thunderbird, go to "Tools -> Account Settings...". (In a Mozilla Suite/SeaMonkey Mail window, go to "Edit -> Mail & Newsgroups Account Settings...".)
- Click the "Add Account" button. Select "Newsgroup account", then put in your name and email address, then put in the newsgroup server, go with the default Account Name (if you want), then finish.
- Click on "Outgoing Server (SMTP)" on the left side. Type in the SMTP outgoing mail server that you use, if you have one. (If you don't, then just forget this step. If you use multiple SMTP servers, read this.)
- Under the name of your newsgroup server (on the left side), select "Server Settings". "Use secure connection (SSL)" and that "Always ask for authentication when connecting to this server" should only be selected if the server requires it. If you can't find anyone who knows what the proper settings are you may have to experiment here. Now click "OK".
- Click your newsgroup server on the left side of the main window. Click "Manage newsgroup subscriptions" in the main right window: this is where you'll subscribe to all the different groups. You may need to click on the little "+" to see all the groups! Subscribe to everything you want.
- Once you've subscribed (checked off) everything you want, click "OK". Double click your newsgroup server on that left side to show you all the various forums and their messages. Click a forum to see a message inside.
- To make a new post to a group, click the group, then click the "Write" (or "Compose") button that's on top.
- To reply to a post, select the particular message and click the "Reply" button up on top.
- When you're reading posted topics, you may have to click on the "+" to expand the thread to see all the responses.