Hello Joe,
Thanks for writing in!
You do not need to edit anything to add an image below the navigation menu. Since the child theme is set up, please add the following code in your child theme’s functions.php file
// Displaying custom image and link under the nav menu
// =============================================================================
function add_custom_image_link(){ ?>
<div class="custom-image-link mam pas">
<p><a href="#your-link-here" title="Your Link Title"><img src="//placehold.it/300x300" /></a></p>
</div>
<?php }
add_action('x_after_view_global__nav-primary', 'add_custom_image_link');
// =============================================================================

We would loved to know if this has work for you. Thank you.