I have not integrated BRouter in Kurviger yet, so there are not more details.
When its implementation time comes, we can announce how it can be used.
It has special workflow, for reference can check some other app guides, e.g.:
https://osmand.net/features/navigation-profiles#create_brouter
https://docs.locusmap.eu/doku.php?id=manual:faq:how_to_navigate_offline