How to deindex a single url?

[Antonio]

You can try checking these, I think they have decent explaination how it works:
<!-- m --><a class="postlink" href="http://www.robotstxt.org/robotstxt.html">http://www.robotstxt.org/robotstxt.html</a><!-- m -->
<!-- m --><a class="postlink" href="https://moz.com/learn/seo/robotstxt">https://moz.com/learn/seo/robotstxt</a><!-- m -->