The auto settings will work reasonably well, assuming a couple of things:
1) that you are within the range of distances covered by that range (e.g. your subject is between 3 and 20 feet away from the camera); and
2) that you are in an environment with some surfaces available (floors, walls and ceilings) to reflect at least some of the light on to the subject.
Regarding number 2, if you are in something like a gymnasium with no walls or ceiling nearby, you need to experiment with your flash. Some flashes have auto exposure functions that over-expose in that environment, while others under-expose.
Have fun.