Instructions
Travel to the Kimono Sisters in Ecruteak City. They will be located in the same location as they were the first time you battled them, near the center of the city.
Press the "A" button to speak to the trainers. A dialog will occur between your character and the Kimono Sisters asking you if you want to battle them.
Click "Yes" by tapping the touchscreen. You will then begin a battle with the Kimono Sisters again.