This is the same way to add google analytics
Go to your site -> Site settings -> Build & deploy -> Post processing -> Snippet injection
Click the drop down -> hit before body.
To save you some time here is the code I use to dynamically inject the ads.
This script will include the google ad scripts. wait 800 ms and add the google ad block to your sidebar. wait 1.5 sec to start serving ads.
These times could be shortened, but i put them this way to ensure the page is fully loaded.
<script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=YOUR-AD-ID"
crossorigin="anonymous"></script>
<script>
setTimeout(() => {
document.querySelector(".sidebar-links").appendChild(document.createElement("div")).innerHTML = '<ins class="adsbygoogle" style="display:block" data-ad-client="YOUR-AD-ID" data-ad-slot="1001042129" data-ad-format="auto" data-full-width-responsive="true"></ins>'
}, 800);
</script>
<script>
setTimeout(() => {
(adsbygoogle = window.adsbygoogle || []).push({});
}, 1500);
</script>