Users underneath blog posts?

“Normal” themes have that out of the box. You have to insert Template_Tags/the_author in the template files – index, single etc.

It might be just commented out – take a closer look.

As I said: look in the them folder (in your case wp-content/themes/default/
and make the changes in the files where you ned the author’s name:
index.php
single.php
archive.php

Here is a quick draft when the different template files are used:
http://www.transycan.net/blogtest/2005/03/31/visual-anatomy-of-a-wp-15-theme/
See also Template_Hierarchy