User-ID setup in GA4

1. Sign in to Google Analytics.
2. Click Admin, and navigate to the property you want to edit.
3. In the Property column, click Default Reporting Identity.
4. Select either By User-ID and device (default setting) or By device only.
5. Click Save.

Reference: https://support.google.com/analytics/answer/9213390?hl=en&ref_topic=9303474