Any tips/advice on losing weight?

My name is Angela and I am 15 years old..I weigh 189 pounds and I am obese. I will be starting my sopre year of high school, and I would like on my 16th birthday to be able to wear a bikini. Do you think it is possible for me to lose that significant amount of weight? I really do want to get into a bikini again and to finally get a belly on ring. So please do not leave any harsh comments and give me real advice. I just think it is finally time to do the right thing...