Go to the News section and your Activity Stream. At the right sidebar you will find an action named "Subscribe to feed".
After clicking this link it depends on your browser what you will see. Some browsers show already styled feeds, other show you just the plain file structure. Nevertheless, you can use the URL including the token as shown in the picture to add this feed to your favourite Feed Reader. You may have already discovered that we provide the more modern ATOM Feed, rather than a RSS feed.
Copy this link into your favorite Reader.