[HELP] controlling wheel collider via touchscreen

Hye guys,
I'm still kinda new. I managed to build a working terrain car using wheel colliders.

I just noticed that the controls are kinda hard coded though? You just write some lines like...

wheelCollider.motorTorque = torque;
wheelCollider.steerAngle = steer;

and the car magically starts to work when you press arrows for steering and throttle.

[QUESTION]
My question is how to adjust the momentary throttle and steeringangle of the wheels via script so I can control the car via touchscreen (in an android game for example)

Ty for directing me the right way.

A.

 

still no idea how to override the arrow controls?