Your tracking script can be installed through the code injector. Every web template we provide has a preinstalled injection code input. To locate it, either click your avatar menu, or visit your website.
Make sure you are signed in with the same account you are installing the script onto.
If you are on the customize, click the button to open up the toolbox. Scroll down to the bottom, and locate 'Code injector':
Click on it – a new modal will pop up with an input in it to paste your Google Analytics code:
Don't forget to save the code!
Make sure you wrap the tracking code inside a script tag. Eg: <script>script code.</script>