How to add a favicon to gh-pages theme

I’m new to jekyll and would like to set a favicon for my gh-pages site however the site is using the cayman template and therefore I’m using markdown so I’m not sure how I would go about setting the favicon can anyone help me?

Add this to your head:

<link rel="shortcut icon" type="image/png" href="/img/icon-192x192.png">
<link rel="shortcut icon" sizes="192x192" href="/img/icon-192x192.png">
<link rel="apple-touch-icon" href="/img/icon-192x192.png">