You're somewhat unlikely to run a stepper with an FRC control system. If you really really wanted to, you'd need to wire two speed controllers up to the stepper and then come up with a class that would cycle the speed controllers through a step cycle on command etc, etc. It's really not worth it.
It should also be possible to get a dedicated stepper controller and control it via DIO pins, much like we do with the parallel port of a PC.