This is your Network Tab. If you get lost, you can click this link to bring yourself back here.
This is a bit like the Newsfeed at Facebook or the Stream at Diaspora. It's where all the posts from your contacts, groups, and feeds will appear. If you're new, you won't see anything in this page, unless you posted your status in the last step. If you've already added a few friends, you'll be able to see their posts. Here, you can comment, like, or dislike posts, or click on somebody's name to visit their profile page where you can write on their wall.
Now we need to fill it up, the first step, is to add people you already know from Facebook.