The Help says:
it is recommended to use the "CityEngine Template Project for Unreal" which is available at the Epic Marketplace (simply search for "CityEngine").
But nothing is found on UE4 Marketplace.
Perhaps it has been removed.
If you have author information or the original link to the reference, I would suggest contacting them
The template project is tied to Unreal Studio. It appears int the Vault of the Epic Games launcher.
For more information on the topic, have a look at this post: https://community.esri.com/docs/DOC-10901-cityengine-exporter-for-unreal-engine-quick-start
Thanks - I was in Linux and the UE4 launcher is on Windows and Mac only. Will check those.