First up, you’d need to register your secondary navigation in functions.php, using register_nav_menus(). You’ll see the existing nav in there, towards the top of this file.
You’d then need to update header.php to add the menu within the banner. Something like this should do the trick…
<div id="bannercontainer">
<div class="banner row">
<nav id="secondary-site-navigation" class="secondary-navigation" role="navigation">
<?php wp_nav_menu( array( 'theme_location' => 'secondary', 'menu_class' => 'secondary-nav-menu' ) ); ?>
</nav> <!-- /.site-navigation.main-navigation -->
</div> <!-- /.banner.row -->
</div> <!-- /#bannercontainer -->
* You’d need to define that theme_location when you register your menu and obviously add in the appropriate styles to style.css
