Hi Amanda,
Thank you for writing in, while that is outside the scope of support, I could point you in the right direction with the understanding that it would ultimately be your responsibility to take it from here. But I see your X Theme (4.6.4) and Cornerstone (2.1.3) is not compatible and that will most likely will cause you an issue in the future. So first, I would advise that you update your X Theme and Cornerstone to the latest version (5.2.5 & 2.1.7 respectively)
Updating Your Themes and Plugins
Follow the Manual X Update Via FTP guide because the automatic update does not work on your current version of X Theme.
Remember to clear all caches (plugin, server-side, CDN, and browser’s cache) after updating so that the code from the latest release is always in use. This will help you to avoid any potential errors.
After you successfully update your X Theme. The file _navbar.php is under /wp-content/themes/x/framework/legacy/cranium/headers/views/global/, copy that file in your child theme (same directory) and open/edit that copied file on a text editor. Locate 2 instances on this line <div class="x-navbar-inner">
and insert your dynamic_sidebar( '' );
function above that line. Then save.
Hope it helps,
Cheers!