RSS feeds

I signed up for Google Reader and also added it to my iGoogle page. I subscribed to the 23 things feed and a couple of other 23'ers,  plus the BBC monthly weather update, Gardners' World blogs, and the VHL blog (which I had never really taken much notice of up until now.) I have yet to work out how to mark an item as unread or how to stick a star on something  - maybe someone can enlighten me? It's bound to be something glaringly obvious!