animating a 2d sprite

Hi, I have this sprite with 3 animation but how do i animate them. each of my sprite animation have 12 frame. I chop up the sprite and drag the first idle animation to the game scene and done the same to the two other animation. Now i have three animation and three controller. By default the sprite play the idle animation but how do i change to a different animation using code in mobile. I want to be able to only use one controller and three animation.please help. thanks