A. Start eating foods that are high in protein and low in saturated fat, for instance, peas, rice, chicken, soy beans, protein shakes.
B. Start doing uphills sprints in small intervals to build your cardiovascular system and lung capacity.
C. Start working your core, exercises to search are: Crunches, Reverse crunches, Twist sit ups, Standing wheel roll out, V-up, Russian Twist, Back Extension, Turkish get up, The Bridge, Super mans, Knee hugs, Leg Raises. These exercises should develop the core if implemented correctly into a core program. Use YouTube or Google to search the exercises and make sure you examine the correct form, it's very important to get form correct.
For instance, a starter abs workout would look like this:
Crunches x 20
Reverse Crunches x 20
Twist Sit Ups x 20
The Bridge - 1 minute
Back Extensions x 12
Repeat Circuit 3 times without rest, take 5-10 seconds rest between each set.