How to embed an external cookie solution like iubenda

We have to comply to some laws with regards to the usage of cookies. Here in Europe a service among others is iubenda. They provide me with a code snippet which I have to embed above the HEAD tag of the page. How can I do that?

<script type="text/javascript">
----something in here
<script type="text/javascript" src="//"></script>
<script type="text/javascript" src="//" charset="UTF-8" async></script>

See if the approach described here would work for you (it injects a CSS file, but it should work the same way for a JS import):