You just hit the "Like" button and it should post directly into your wall if you're logged into Facebook. If you're not logged in, you will have to log into Facebook for it to go to your wall.
At the moment, you can't. Blogs do not have the "like" function even though most Wikia pages do have it. In the other pages clicking on "like" will post the link automatically to your facebook account. For blogs, I suggest that you copy the link into your facebook wall instead.