Eat clean and healthy, check workouts which are for your core, your arms, shoulders and legs. And be patient;)
You should focus on strength and endurance. You seem to be quite young so get into healthy habbits. Research and educate yourself. Nutrition and training. All things will come in due time my friend.
3 days/wk basic weight training working large compound groups of muscle.
Beginner Weight Training: Workout A
Beginner Weight Training: Workout B
If you don't have equipment use Google to find equivalent exercises you can do. For example, if you don't have dumbells, you could search "shoulder press alternatives"
Combined with every other day doing mad cardio. Long workouts are ok but HIIT comes highly recommended. Jumping rope is great for convenient little free time bursts of burning max calories & burning calories is what you need to get your body fat percentage down to visible ab levels.
2.5 Mins Of Cardio (Jumprope) In 4 Mins Of Tabata Intervals
And every day eating super clean. This is probably the most important part, with core workouts being the least important. People always want it the other way around though.