How to add a new menu item in "Twenty fourteen" theme?

Hello!
I’ve created two menus inside of my theme’s functions.php file:

register_nav_menus( array(
‘primary’ => __( ‘Top primary menu’, ‘twentyfourteen’ ),
‘secondary’ => __( ‘Secondary menu in left sidebar’, ‘twentyfourteen’ ),
) );

I’m trying to figure out how to add additional menu items which are not necessary lead to pages inside of the wordpress. In my case, they are more likely to lead on external resources, so it probably would look like:

<div class=”menu-item”>
<?php _e( ‘Item’, ‘twentyfourteen’ ); ?>
</div>

Is it possible to perform in the header.php file?