Si no me equivoco, basta con añadir en el sector que quieras este fragmento:
<?php
$today = current_time('mysql', 1);
if ( $recentposts = $wpdb->get_results("SELECT ID, post_title FROM $wpdb->posts WHERE post_status = 'publish' AND post_date_gmt < '$today' ORDER BY post_date DESC LIMIT 10")):
?>
<ul>
<?php foreach ($recentposts as $post) {
if ($post->post_title == '')
$post->post_title = sprintf(__('Post #%s'), $post->ID);
echo "<li><a href='".get_permalink($post->ID)."'>";
the_title();
echo '</a></li>';
}?>
</ul>
<?php endif; ?>
Esto probablemente sea en sidebar.php dentro del theme editor (vía admin panel).