I want to be able to use the motor as a step motor...
As MarkT said, you can not use the motor as a stepping motor only as a servo motor. And that is not the sort of hobby servo motors you get where you can set a fixed angle. This is because there is no gearing between the motor and the position indicator and you do not have very fine control over the motor.
With a stepping motor it can be static with full holding torque and you can move it in increments. You can not do this with the motor you have.