Easy-peasy!

1 - Log in.
2 - Click on "post something!"
3 _ Choose "story" (that's the front page news) - or "Print" "Radio" "Commercials" if you're uploading your work.
4 - Type away!

A basic understanding of how to create links in HTML is useful. But if you want to link a twitter-user simply write an @ - that at-sign makes an automagic link. So does the # pound-sign if you want to link a twitter hashtag.