Answer:
You need 3 things to download from Usenet.
The first is a Usenet Newsgroups provider, such as Newshosting or Giganews. These providers charge for access but you can get free trials to start you off. It should be noted that the free providers are rubbish as you get incomplete files and slow speeds.
The second thing you need is a Usenet client such as Grabit or SABnzbd, both are totally free.
The third and last thing you need are NZB files, think of these as torrent type files except for newsgroups.
For complete details on how to download - please visit http://usenetdownloadguide.com