Ubermenu plug-in customiser not working

Hi there,

I was wanting to have some CSS coding additions for my site's menu, and followed one of the recommended articles where you guys have suggested Ubermenu. Trouble is, I can't get it to work.

I'm following the ubermenu instructions for overwriting the .php file:
and trying to replace the normal nav menu. Where is the navigation menu code located and what is the best way to override it in a child theme?

They suggest:
<?php if( function_exists( 'ubermenu' ) ): ?>
<!-- UberMenu integration code goes here -->
<?php else: ?>
<!-- Existing Theme Menu code goes here -->
<?php endif; ?>

Also, when I click on the ubermenu customiser it doesn't work (takes me to the themes page)

Kind regards,