They start with adding a comments summary to the page, giving the user a view of the previous comment submitted by other users. They include a brief look at anchor tags before moving into the code to display some of the previous blog entries. Next up is all about getting more specific - creating the code to view each of the specific blog entries.
Of course, what is an entry without its comments, so they include the code to integrate that into the page as well. Finally, they give the user a way to talk back about the content they're reading by adding a simple comments form to each of the posts' pages.