A blog, or web log, features a homepage with a list of news items, ordered from most-recent to oldest.

To make your site operate as a blog, login choose the "Edit" tab in the green-shaded actions. Click on the [news/events] link to display news options. Check the Show News on Homepage box and uncheck the Show News Portlet box.

Pick a number of news items to display on the home page via the Homepage News Item Limit option.