You cannot spot reduce fat from specific areas of your body. The only way to lose fat generally is by eating a healthy, balanced diet, lower in saturated fats and sugars.
Participate in Cardiovascular exercise at least 3 times per week and do some resistance training. Your heartrate needs to stay at between 134 and 164 beats per minute, for at least 20 minutes per session. Although you can use weights, your bones are still growing, so caution should be exercised and advice sought.
You can still use your own body weight to tone muscles. Try doing press ups (start on knees) tricep dips, lunges and squats. Use a Stability ball for doing stomach crunches, you can also use it against a wall for squats and also for press ups.