Launching a Mailchimp popup from a menu item

I found solution using bootstrap popup and mailchimp shortcode.

You need to install mailchimp plugin.
https://wordpress.org/plugins/mailchimp-for-wp/

Step 1 : Customise menu item

function nav_replace_wpse_189788( $item_output, $item, $depth, $args ) {
 //var_dump($item_output, $item);
    if( $args->theme_location != 'main_menu' ){
        return $item_output;
    }

    if ( $item->menu_order == '3' ) {
        $item_output .= '<li class="moblie-nav menu-item menu-item-type-custom menu-item-object-custom last-menu-item">';
        $item_output .= '<a href="https://wordpress.stackexchange.com/questions/338839/JavaScript:Void(0)" data-toggle="modal" data-target="#myModal">Subscribe</a>';
        $item_output .= '</li>';
    }

    return $item_output;
 }
 add_filter('walker_nav_menu_start_el','nav_replace_wpse_189788',10,4);

Step 2 : Add popup with mailchimp shordcode

<!-- Modal -->
<div class="modal fade" id="myModal" tabindex="-1" role="dialog" 
   aria-labelledby="myModalLabel" aria-hidden="true">
   <div class="modal-dialog">
      <div class="modal-content">
         <div class="modal-header">
            <button type="button" class="close" data-dismiss="modal" aria-hidden="true">
                 <img src="https://wordpress.stackexchange.com/questions/338839/images/close-icon.png">
            </button>
         </div>
         <div class="modal-body">
            <div class="exp_login_wrap">
                <h3>Subscribe</h3>
                <?php echo do_shortcode( '[mc4wp_form id="26125"]' );?>

            </div>
         </div>
      </div><!-- /.modal-content -->
   </div><!-- /.modal-dialog -->
</div><!-- /.modal -->