But I dont really know how I'm gona manage this with the code abowe.
Do you KNOW what that code does? Have you made changes and observed the effects?
If so, making the motor step once each time you press the switch is trivial.
You are stepping one way while the switch is held down (assuming you wired the switch correctly) and stepping the other way when the switch is released. Is that what you want?
What does that code actually do, and how does it differ from what you want it to do?