foundation-topbar-menu.php and foundation-topbar-walker.php should be required in the WordPress functions.php file.
The code in foundation-topbar.php should be added below the body tag in header.php
Setup a menu in WordPress admin under Appearance > Menus
Use the 'label' class on a menu item to create a menu section title
Foundation Top Bar Doc: http://foundation.zurb.com/docs/components/top-bar.html
@aweshout I used the function you wrote to add a search input to the right menu, and it is not showing up in the top bar menu. I added the function inside foundation-topbar-menu.php. Was that the wrong place to add it?