Captcha in Comment Section

Hi there,

I love your awesome theme and I’d like to implement a Captcha in the comment section for commentators.

The one I’d like to use is this one: https://www.ads-software.com/plugins/alobaidi-captcha/

How is it possible to implement the Captcha. I Alreday looked into comments.php and /include/comments.php

Any hint for me? Thx in advance.