Simpler style for Disqus theme "Narcissus"

discuss_simpler_narcissus.css

/* ------------------------------------------------------------------------------ 
   Simpler style for Disqus theme "Narcissus"

   Use it in your website stylesheet or add to Disqus 
   (Settings > Customize > Custom CSS).	

   Author: Martin Michalek, michalek@shortcat.cz, www.vzhurudolu.cz
   ------------------------------------------------------------------------------  */



/* = Not showing some elements = */

/* "Showing X comments" heading */
#disqus_thread #dsq-content h3,

/* "Sort by..." select input */						
#disqus_thread #dsq-content .dsq-item-sort,

/* E-mail subsription icon */
#disqus_thread #dsq-content .dsq-subscribe-email img,

/* RSS subsription icon */										
#disqus_thread #dsq-content .dsq-subscribe-rs img,

/* Hide thread icon */
#disqus_thread #dsq-content .dsq-full-comment .dsq-comment-hide-thread,

/* Like comment icon  */
#disqus_thread #dsq-content .dsq-comment-footer-right .dsq-like,

/* Trackback URL */
#disqus_thread #dsq-content .dsq-item-trackback
  { display: none; }



/* = Simpler look and feel = */

/* "Comments are not allowed" and other messages  */

#disqus_thread #dsq-content .dsq-remove-message, 
#disqus_thread #dsq-content .dsq-realtime-alert, 
#disqus_thread #dsq-content .dsq-missing-permissions p {
	border: 0;
	background-color: #eee;
	color: #666;
	padding: 10px 10px;
	margin-bottom: 1.5em;
}

/* Repair toolbar dropdown z-index */

#disqus_thread #dsq-content #dsq-toolbar-dropdown {
	z-index: 100;
}

/* E-mail and RSS subscription anchors */

#dsq-content .dsq-options {
	padding-bottom: 5px;
	background-color: #f8f8f8;
	padding: 10px 10px 7px;
	margin-bottom: 1.5em;
}

#disqus_thread #dsq-content .dsq-options .dsq-subscribe-email {
  margin-left: -5px;
}

/* E-mail and RSS subscription anchors */

#disqus_thread #dsq-content .dsq-options .dsq-subscribe-email {
  margin-left: -5px;
}

/* Comment header */

#disqus_thread #dsq-content .dsq-comment-header {
	border: 0;
	background-image: none;
	border-bottom: 2px solid #ccc;
	padding: 10px 5px 5px;
	-moz-border-radius: 0; /* [OBSOLETE] in FF4 */
	border-radius: 0;
}

/* Moderator's comment header */

#disqus_thread #dsq-content .dsq-moderator .dsq-comment-header {
	background-color: #f8f8f8;
}

/* Anchor hover color 
   NOTE: use your own anchor hover color 
*/

#disqus_thread #dsq-content a:hover,
#disqus_thread #dsq-content a:active {
	color: #2f510b;
}

I think they have changed the UI up a bit. Where do I put the custom CSS now?

@CoolAbhi1290 Thanks for the comment, but this is really (really!) piece of code — was created 9 years ago.
The gist has nothing to do with current Disqus styling.