First choose 'Pick Up Game' then choose to be 'Home' or 'Away' then enter your name then press A then A again and when it says 'Enter Code Now' on the bottom of the screen hold L and press a button combination while holding L.
For example:Hold L and press Y,Y,X,B,X,B,B,X. When you do this you will unlock two things at the same time.You should here a car beep after each 4 button pressing.For(another)example: Y,Y,X,B,Then car beep,X,B,B,X,Then another car beep. This is how you Double Code Enter.