Add a feed, search for a feed or browse the directory…you are allowed a max. of 5 feeds in your feed set.
You can also browse for feeds by tag, if you add a tag feed to your map, this means you are subscribing to all these feeds in one go (kind of has an OPML feel about it, in fact they use the OPML icon).
The reason you can browse feeds by tag is that when people add a feed to the directory they can specifiy up to 3 tags to describe it.
Anyway, to read the feeds you will see a world map, where ever a feed is geographically based is where it will appear in the map, just hover over the red dots, and a box will come up showing titles of the latest posts, click one to go to the native site.