The first episode of The Fate of Atlantis - Fields of Elysium - starts with a quest called The Isu Beckon.
After installing the content and entering the game world via The Fate of Atlantis menu, you should have access to a fast travel point Gateway to the Lost City located near the Volcanic Islands. 
If you cannot see The Fate of Atlantis button in the main menu, please make sure your content has been correctly installed.
Additional help with checking whether the content has been installed on your platform is available in our dedicated articles:
Do not hesitate to reach out to us if you continue having problems with accessing the content or have any other questions.
After installing the content and entering the game world via The Fate of Atlantis menu, you should have access to a fast travel point Gateway to the Lost City located near the Volcanic Islands.
Location of the fast travel point
On arrival, you should see a New Quest prompt, after which The Isu Beckon will be added to your quest journal.
If you cannot see The Fate of Atlantis button in the main menu, please make sure your content has been correctly installed.
Additional help with checking whether the content has been installed on your platform is available in our dedicated articles:
Do not hesitate to reach out to us if you continue having problems with accessing the content or have any other questions.