While logged in, hover over or click the “Posts” menu item in the left-hand sidebar menu. You should be given the option to edit “All Posts” or make a new post. Your blog has a default first test post. If you edit it, you’ll be able to see how posting works.
Edit the post and save it. Then you should be able to visit both your blog’s home page and the home page for thirty//thirty and see your test post there.