To Use CityEngine you must have a valid license in the form of a Named User license. A Named User license is applied to an organizational user in either ArcGIS Online or ArcGIS Enterprise organization.
When starting CityEngine, the Configure Licensing Portal pane of the ArcGIS Sign in for CityEngine dialog box displays and you will be asked to sign in with the licensed user:
Sign in to either ArcGIS Online or ArcGIS Enterprise and click OK.
The Sign in pane displays:
Provide your credentials to sign in and click Sign in. CityEngine starts with the Named User license just created.
Check the Sign me in automatically check box to have CityEngine start without the sign-in prompt the next time you open it. Click Configure Licensing Portal to change the licensing portal. Click Sign in using browser when the account configuration doesn't allow signing in through the CityEngine dialog box. When you sign in with a social login ( (GitHub, Facebook, Google, or Apple), the sign-in is authenticated by the system browser. See sign in with a social login for more information.