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Here you can read an article about how to upload and download binary files to a newsgroup, and handle yEnc encoded posts.
If you are mainly interested into pictures and movies, visit the Gigantic Usenet Binaries Archive, a huge archive of binary files from the newsgroups, automatically downloaded, thumbnailed and indexed in categories, with no IP logging. Half a million images and videos with 50'000 new ones every single day.
If you want full access to over 100'000 uncensored newsgroups, you can get an account on Alibis, that gives you full Usenet access, respecting your anonimity and privacy (no IP logging of uploads nor downloads), and gives you more features, like newsgroup search, for a very low price.