Implementation of CLARITY within custom themes in Guide

I am trying to implement Clarity which is  a free behavioral analytics tool Microsoft.

The setup requires adding some code:

Instructions state to copy and paste the Clarity tracking code into the </head> element of the site. I'm not sure where to enter this (file and location in file)

Has anyone had experience with Clarity or could point me where I would need to add this snippet of code?

Clarity tracking code

<script type="text/javascript">    (function(c,l,a,r,i,t,y){        c[a]=c[a]||function(){(c[a].q=c[a].q||[]).push(arguments)};        t=l.createElement(r);t.async=1;t.src="https://www.clarity.ms/tag/"+i;        y=l.getElementsByTagName(r)[0];y.parentNode.insertBefore(t,y);    })(window, document, "clarity", "script", "l9fahiwool");</script>