www/_includes/about.html

<div class="remove-container container-block">
<h2 class="container-block-title">About Theme</h2>
<ul class="list-unstyled interests-list">
<a target="_blank" href="https://www.youtube.com/watch?v=Jnmj1dXDbNk"><li>How to use?</li></a>
</ul>
</div><!--//About-->