The iTunes Genius functionality offers iTunes users two great features: automatically generated playlists from their libraries that sound great, and the ability to discover new music at the iTunes Store based on the music they already like.
In order to use these features, though, you need to set up iTunes Genius. Here's a step-by-step guide to how:
Begin by downloading and installing iTunes 8. When that’s done, launch it and look for the Genius icon in the left-hand tray.