Embed buttons in posts grid

I want to add the Add-to-Any short code to a php file that handles my news grid layout. I don;t know php all that well so i need help in adding the code to this php snippet where i indicated below:

$return_string .= ‘<section class=”post-content”>
<h2 class=”post-heading”>’. get_the_title() .'</h2>
<div class=”post-meta”>
<span class=”author”>
<i class=”fa fa-user”></i>
‘ . get_the_author() . ‘
</span>
<span class=”post-date”>
<i class=”fa fa-calendar”></i>
‘ . get_the_date() . ‘
</span>
</div>
<p>’ . strip_shortcodes(wp_trim_words( get_the_content(), 25 )) . ‘ <span class=”text-muted”></span></p>

<p>
Add Add-To-Any code here
</p>
</section>

I am trying to add the share links to the Blog post grid at the bottom of this page:

http://avc2.warnickdesigngroup.com/

Thanks for any help!

https://wordpress.org/plugins/add-to-any/