Q: How do I leave from Cyrodiil?

Though Cyrodiil has a fast-travel system with waypoints / wayshrines, it’s not connected with any areas outside Cyrodiil.

To leave Cyrodiil you will need to visit the starting area of your faction. Only there can you interact with a wayshrine which can take you outside of this zone. The map below shows the locations of wayshrines that can teleport you outside of Cyrodiil:

Visiting one of these gates and interacting with a wayshrine can teleport you out of Cyrodiil