Trio comes with Disqus integration. Trio contains all the Disqus Javascript and HTML code required to make Disqus work. All you need to do is change the disqus_shortname field in _config.yml.

To get a disqus_shortname, you’ll need to sign up for a Disqus account.

While testing on your local machine, you might want to enable developer mode for Disqus by setting the Javascript disqus_developer variable to 1 in index.html and _layouts/post.html files:

var disqus_developer = 1; // Comment out when the site is live

Remember to comment out the lines when making your website live.

There is a delay (about 5-10 minutes) between setting up Disqus correctly and seeing the comments and comment counts show up. For more details or to understand how Trio adds Disqus comments, see this post.