Instructions
Begin a new game in the mode of your choice.
Select Princess Peach in the character select menu by placing your token over her picture.
Click the picture of Princess Peach with your cursor to change the color of her costume. Alternately you can press either the "1" or "2" button if you are using the nunchuk control scheme or "X" or "Y" if you are using a classic controller or Gamecube controller.
Cycle through the costume choices until you reach the Daisy outfit, which is a yellow dress with brunette hair.
Press the "start" button to begin your match as Peach wearing a Daisy costume.