Using Undicat Analtics with Gatsby requires no extra configuration. If you have some sort of automatic build set-up, you'll need to find a way to get the script onto the page. Otherwise, the following code, added to your index.html page will do the trick.
<script src="https://cdn.undicat.com/analytics.js" spa="auto" apikey="ABCDEFGHIJKL" defer></script>
To learn about all the options we offer, read our advanced documentation here.