Lots of ways to do this out there, ranging from “too much code” to “but, why?”. Here’s how I chose to do mine:

<script>
$(function() {
   var footer = $('.post-footer');
   if (footer.length) {
       footer.after('<div id="disqus_thread"></div>');
       (function() {
			var d = document, s = d.createElement('script');
			s.src = 'https://!!!YOUR_ID_HERE!!!.disqus.com/embed.js';
			s.setAttribute('data-timestamp', +new Date());
			(d.head || d.body).appendChild(s);
		})();
   }
});
</script>

This goes into the footer, in the code injection tab.