I will join the rest in recommending that you get rid of that junk motor driver and get a driver made for that type and size of motor. Power supply as well.
Here are a couple of tutorials that may be helpful.
Stepper motor basics.
Simple stepper code.
And you may at some point want a library that will help to control the stepper(s). I like the MobaTools stepper library. It is available for installation via the IDE library manager.