From the settings panel, click Go to Google Reader. From this page, you can click Take a Tour, or

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watch a video a Google engineer, Chris Wetherell, tell all about Google Reader. If you’re new to feed readers, both those options are worthwhile. For those who are familiar with feed readers, it’s really unnecessary to bother with the tour and video. When you’re ready, click “
Get started by adding subscriptions.” Google has some pre-selected bundles of feeds in a few different categories. Newbies should select one of these to play around with Google Reader a little bit. This page also allows new users to quickly add feeds from Flickr, Blogger, del.icio.us, Live Journal, Windows Live Spaces, Xanga, Wordpress.com, and Myspace by typing in a username, selecting a website from the pull down menu, and clicking Subscribe.
If you’ve been following through, step-by-step, then you’re Google Reader account is all set up and ready to use. Whenever you see a little orange RSS link, click it to add to Google Reader.