In addition to discussions Usenet news is also a repository for a great number of multimedia and binary files, including images and MP3 files. Once you have your software you need to configure it to connect to your news server. Usually subscription just means that you will develop your own list of newsgroups that interest you to keep you from having to search through 50,000 group names every time you want to read messages. You can post new articles to a group and you can reply to posts. Be sure to get a flavor of what a group expects in a post.
Some newsreaders require a response post to be a certain size relative to the original.
Some newsgroups are moderated with all posts being screened by the moderator.