Never known how. Do you have to get a server from your ISP or are there open servers like IRC has?
I haven't used them in years, but your ISP should have a news server you can connect to. Most email programs are set up so you can use them as news clients as well.
I just remembered that there was a newsgroup search engine called Deja....just went to check it out, and apparently it is now owned by Google.
If you want to search newsgroups via Google, just go to the home page and click on "Groups".
I will check with my ISP. I don't think that Google allows you to view the user groups through your mail application which I want to do.
I wonder if they are still popular. I haven't used them in 4 or 5 years.