Create a include .php into \yoursitename\sites\all\themes\yourtheme\templates\include\prop-sidebar.inc.php
Open the master .php file where the above include file to be included.
Add the following line to include the file
<div class="col-md-3"> <?php include(drupal_get_path('theme', 'sello') . '/templates/include/prop-sidebar.inc.php'); ?></div>