RSS stands for "Really Simple Syndication".  It is a method of publishing frequently-updated content to the web.  Those who want to read RSS content use programs called "aggregators" to access it.

RSS feeds provide a way for users to see if their games (or if forums they read) have been updated without them necessarily visiting RPoL.  Now, that's all that can be checked: as RPoL only knows your access within a game when you enter that game, the most that can be provided is an indication that a game has been updated.  To read the update, you'll need to visit RPoL.

To read an RSS feed you must subscribe to it.  This requires using a bit of software called an "aggregator".  Some browsers have one built in, and so can bookmark RSS feeds as "live bookmarks".  Many mail clients also allow subscriptions to RSS feeds and will deliver updates through the client.  Still, some people prefer to use a dedicated RSS Aggregator.  These can easily be found using a search engine.

As the subscription method may vary from one software package to another, the best way to learn to use it is by reading your aggregator's help files.

Under your User Preferences setting you'll see a link for "RDF / RSS / Atom Feeds".  These are all basically the same thing, though they use slightly different standards.  Use the appropriate link to subscribe with your RSS Aggregator.

Additionally, web browsers which automatically discover RSS feeds should alert you to your personal feeds when you visit the Main Menu.  If this is the case, you'll see an icon indicating this in your browser's address or status bar.  Most commonly, the icon is a small orange square like this one:


In such browsers, clicking on the displayed icon will usually open a dialog so that you can subscribe to the feed.