In case you don't already know, when you go into a board, all of the post topics appear newest first. Before any of the posts is a line with titles for each column: Subject/Started by; Replies/Views; and Last Post.
If you click on any of these words, the topics will be sorted accordingly in ascending or descending order. Click again to reverse from ascending to descending and vice versa.
For example, click on Subject and all topics will be sorted by Subject titles.