Don't ask me why, but it really is usenet, not newsnet!
I currently have no news-access, therefore this info might be a bit outdated. In order to use the usenet, you need a newsserver. Some providers include a newsserver in their services, some don't.
The news-provider also selects which list are offered, not every server has
every newsgroup. Newsgroups are sorted by topic, good newsclients will give you a way to search the available groups for keywords.
Note: Some time ago, I was reading the debian-user mailinglist via news, however, note that you can't post to those gateway-newsgroups with a newsclient.