How to start station self-clean?

1.When the robot is in the Station, press and hold return button,the robot will automatically exit from the station, and washing tray will automatically add water. 2.Use cleaning tool to clean the mop washing tray. 3.About 1 min later, the Tray will automatically drain the dirtywater. 4.Pour the dirty water out. 5.Short press the return button to make the robot back to the station, make sure that you hear 'start charging'.