If you have a Google Analytics account, you can add the tracking code into your direct booking website by navigating to Menu > Website Builder > [select website] > Edit Website > 3rd Party Integrations. See more details about 3rd party integrations here.
Note:
Google Analytics Universal has been deprecated and replaced by Google Analytics 4. If you've been using Google Analytics Universal, simply update your Universal tag, beginning with UA-XXX, to the Google Analytics tag G-XXXX. This tag is readily available in your Google Analytics 4 account.