Promoting a post allows the author to bring attention to a particular post and brings the post up to the top of the main blog page. Promoting a post also subtly highlights the post with the primary theme color and there will be a loudspeaker icon at the top of the post to mark this as a promoted announcment. To promote a post, open up a post in the Post Interface, click on the Promote checkbox underneath the Post Editor, and click on the submit button. 

Deselecting the Promote checkbox will return the post to its original location sorted by the Post Sort Date or by the Date Posted.