GIF as featured image in Enfold theme

How can I use a GIF animation as featured image

I found this piece of code, where it will insert the GIF, without changing the size, so that the GIF will show as featured image. If JPEG or other image file, it wil recize.
But where to put the code, or is there any other way to use GIF animations inside the Enfold theme?

<?php
$url = wp_get_attachment_url( get_post_thumbnail_id() );
$filetype = wp_check_filetype($url);
if ($filetype[ext] == ‘gif’)
{the_post_thumbnail(‘full’, array(‘class’ => ‘img-responsive’)); }
else
{the_post_thumbnail(‘medium’, array(‘class’ => ‘img-responsive’));}
?>