Embedded script within the head tag of website template:

Hello, I need to add this script "embedded within the head tag of your website template."

<script>
(function(d) {
var el, fjs = d.getElementsByTagName('script')[0];
el = d.createElement('script');
el.id = "js-pp-banner";
el.src = "//dashboard.presspatron.com/dev/banner?b=pDdnuTj1qkSY5zbNnj9WuuTN";
fjs.parentNode.insertBefore(el, fjs);
}(document));
</script>

Can someone please help me figure out how to do that?

Thanks