Include the Jdenticon library somewhere on your page. Below is Jdenticon served from jsDelivr, but you can download and host it yourself as well.
<script src="https://cdn.jsdelivr.net/npm/jdenticon@3.2.0/dist/jdenticon.min.js" async integrity="sha384-yBhgDqxM50qJV5JPdayci8wCfooqvhFYbIKhv0hTtLvfeeyJMJCscRfFNKIxt43M" crossorigin="anonymous"> </script>
Add an <svg> element where you want to render an identicon. Use the data-jdenticon-value attribute to specify that an identicon should be rendered. user127 below is just an example of a value.
<svg width="80" height="80" data-jdenticon-value="user127"></svg>
Refresh the page in your browser.