With this bundle you can use all con4gis 3.5.x extensions with Contao >= 4.2.x
Before you can start using the the con4gis extensions, please be sure you've added the new route to app/config/routing.yml You have to add the new route before the contao routes.
Con4gisApiBundle:
resource: "@Con4gisApiBundle/Resources/config/routing.yml"
ContaoInstallationBundle:
resource: "@ContaoInstallationBundle/Resources/config/routing.yml"
ContaoCoreBundle:
resource: "@ContaoCoreBundle/Resources/config/routing.yml"