First tell disqus you are in developer mode so it will allow your local website to load disqus js script, this way:
<script type="text/javascript">
/* * * CONFIGURATION VARIABLES: THIS CODE IS ONLY AN EXAMPLE * * */
var disqus_shortname = 'example'; // Required - Replace example with your forum shortname
var disqus_identifier = 'a unique identifier for each page where Disqus is present';
var disqus_title = 'a unique title for each page where Disqus is present';
var disqus_url = 'a unique URL for each page where Disqus is present';
/* * * REMOVE THE FOLLOWING LINE IN PRODUCTION * * */
var disqus_developer = 1;
/* * * DON'T EDIT BELOW THIS LINE * * */
(function() {
var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true;
dsq.src = '//' + disqus_shortname + '.disqus.com/embed.js';
(document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq);
})();
</script>
After that you can use disqus import feature to load lots of test comments. Also I recommend you to read the best practices.