You can control your buses from the Central Bus Station building. From the Central Bus Station window, you will be able to send buses to your friends’ cities, and receive income for doing so. Upgrade your Central Bus Station and conduct research to receive plans for making new types of buses. The higher the level of your Central Bus Station, the more buses will it be able to house. And, the better the bus, the more stops it can make on its route, and the more income it will earn you per stop.
Have fun playing the game!