You need to do cardio, cardio, and more cardio.  Building muscle is great but if your six pack is under 2" of fat you can't see it without a scalpel.  

When running (or any form of cadio) make sure you keep your hear rate in the fat burning range.  Initially you will want to use a heart rate monitor eventually you will just be able to feel when in the zone.  Running too fast, too hard will spike your heart rate out of the zone.  At that work level your body can't efficiently burn fat and still provide the needed energy so it switches to only burning blood sugar.  So instead you will want to run slower/easier for longer periods of time.    If you are going to run remember running is destructive to the body (literally components are damaged, degraded) so you need off days.  Initially I would say run no more than 3 days a week and eventually you can bump that up to 4 or 5.  

TL/DR version:
If your goal is to lose fat you need to focus on cardioand keep your heart rate in the fat burning zone.  Once you burn off enough fat switch to a more varied work out regiment.