This page applies to b2evo 0.9

In the Main Template, before or after where the post content is displayed, add the following code:

Posted by: <?php $Item->Author->prefered_name(); ?>

If you want to link to all the posts of a certain author you can use this code :

<a href="<?php echo url_add_param( $Blog->get( 'blogurl', 'htmlattr' ), 'author='. $Item->Author->ID) ?>" title="<?php echo T_('Browse all posts by this author') ?>"><?php $Item->Author->prefered_name() ?></a>