This theme comes with Disqus integration.
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.
You can disable comments on a per-post level by adding the following line to YAML front matter
to the post:
comments: false
To get a disqus_shortname, you’ll need to sign up
for a Disqus account. There is a delay (about 5-10 minutes) between setting up Disqus correctly
and seeing the comments and comment counts show up.
This
outdated post describes this in more detail Disqus comments.