Loading Script On Every Page

I am trying to load a script from an ad company on each page and I am struggling to understand how to do it. I have read the following…

I believe what I need to do is get the following header script to fire all the time (on topics… categories… main page… latest… new… unread).

Here is what I need to load…

<script type="text/javascript" src="//monu.delivery/site/5/e/f6315f-ed86-4a10-baea-e03876046885.js" data-cfasync="false"></script>

It seems like this should be fairly easy… but I’m just not fully understanding it yet. Can someone help me out?