Mass effect 3 - kaiden vs ashley how to choose???

Hello all

I was wondering how to get the game so that i have kaiden alenko in game rather then ashley, The option doesnt appear in the prolouge in the choices section. There is no mention of either of them and i keep getting stuck wioth ashley - when i  wanna play the game with kaiden., I dont understand why this i sthe way it is, and can anyone help me make the game start with kaiden on wii u? 

Thankyou 

Mike