On the machine that has both the internal wifi interface (AutoInterface) and connections to nodes on the internet (BackboneInterface or TCPClientInterface), just enable transport, and you're good to go, the smartphone can now reach anything the transport node can reach.
However, to improve your configuration, you should at least set AutoInterface on the transport node to gateway or internal mode, so clients on your internal WiFi can recursively resolve paths (makes getting paths much faster).
Another option is (if you don't want to see the constant stream of incoming announces from the wide world on your internal network) to set the interfaces that connect to the wide world to boundary mode. If you do that, your internal clients will still be able to resolve paths and connect to anything else, but you will only get announces for the destinations they ask for.