I would very much advise against going from zero miles / week of running to a program of 15-20 miles a week of tempo runs at the academy. You need to condition your muscles and joints, not just your cardio, to sustain a program of running like that over a prolonged period of time. Otherwise you can very easily end up with tendonitis, bursitis, shin splints or other overuse injuries that comes with ramping up a program too quickly.
I'm not saying I'd advise running A LOT before the academy, but a general cardio program (however you want to do it) with at least 5 miles of running / week is what I would recommend.

