Alright to get this you need to talk to the 5 npc allies you meet during the game with the right character. Now the order to that is
For kasey in chapter 2 use Donatello. (Gives you double jump)
For slash (The big turtle after you finish the 3rd chapter) use Raphael. (Gives you ground smash)
On the way to the docks use Leonard's to talk to the ninja chick (Karai) (gives you dash)
In the docks you will find April use Donatello (gives you counter).
And lastly in dimension X chapter 7 use Michelangelo to talk to the the big crocodile (Leatherhead) that teaches you to turn invisible.
If you mess up one of the conversations just quit to menu and reload your save you will be loaded in where you last meditated.