I figured it out.
I added template tag code to sidebar.php:
<span class="gat_widget"> <?php _e('Important Resources'); ?></span>
<ul>
<?php wp_nav_menu( array( 'container_class' => 'menu-header', 'theme_location' => 'secondary' ) ); ?>
</ul>
Man, I just dig WordPress. And I am so-not a php coder!!
Thanks for the response!