Watch the fat, sugar and simple carbs in your diet
Make sure you have a caloric deficit
Cardio to lower your body fat percentage (boxing is really intense cardio if your gym has a bag)
Work your abs out to gain definition (upper, lower, sides)
In general, the more muscle you gain the more calories you'll burn when idle which helps increase your caloric deficit. Also, wherever you hold the most fat is the place that will lose it last, there's no such thing as targeted fat loss.
It's not easy, trust me, I lost 60 pounds in the past year but it feels awesome.