I don't know of any code for the TinyShield Motor x4 motor driver to run a stepper motor. There is some code in a forum post that runs a stepper motor from a different dual H-bridge motor driver that you might be able to look through for ideas.
Alternatively, I think there is a good chance you might find it easier to use one of our stepper motor drivers to control your motor. The link you provided is for a one of our discontinued stepper drivers, not a stepper motor. If you let us know which motor you have and the power supply you are using, I can probably recommend a stepper motor driver for it.