First, you need to create an account on Google Analytics and add your website to Google Analytics. See here how you can do this.
1: Log on to your Site Builder
2: Go to Site settings
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3: Click on Google Analytics
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4: Now find your Tracking-ID, you can find your unique Tracking ID at Google Analytics when you have added your website to Google Analytics.
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5: Enter your Tracking ID to your Site Builder
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6: Now click on the Save button, you can find this on the bottom in the right corner of your page
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