In order to add Google Analytics to the Kadence Theme within the Customizer, you need the Pro Version of the plugin*.
Once you have installed the Pro Version, activate “Headers/Footer Scripts.”
Now you will have an area in the Customizer, at the bottom, called “Custom Scripts.”
Place the Google Analytics code in “Add scripts into your header” and Publish.
(*Note: I might receive a commission if affiliate links are clicked on and purchased – at no additional charge to you.)