Add a Google Analytics 4 property (to a site that already has Analytics)
If your website builder/CMS does not use the gtag.js tag, and your current tag is analytics.js.
You will need to create a new property. Make sure to use “enhanced measurement” to keep your prior data.
Goto G4 Setup Assistant
Click Data Stream & click on the G4 listing
Configure tag settings
Copy the gtag.js and add it to your site header pages