This is how to do it if you’re hosting your own WordPress install. Not sure how to do it if your site is hosted by WordPress.
Essentially, you’re going to create a custom version of header.php for Cubic to use. By default, Cubic uses Boardwalk’s header.php, unless you create your own header.php inside Cubic. So, first step, copy header.php from Boardwalk into Cubic in your /wp-content/themes folder.
Now, the menu currently exists in Boardwalk’s sidebar.php. Open that up, and look for a line that says <?php if( has_nav_menu(‘primary’) ) :?>
You’re going to copy everything from the start of that line down to the end of the comment <!–#site-navigation–>.
Now, go to header.php inside Cubic. After the comment <!–.site-branding–>, paste the code you copied from sidebar.php. Save your Cubic header.php.
That should be it. You’ve copied the nav menu from the sidebar to the header. You’ll have to do a lot of css work to get it styled correctly, but the nav menu is in the right spot.