How much weight should I loose? What areas should I target?

poetic-rhythm
So after recently weighing myself again and becoming sick of all the fat jokes I decided that I should probably get my ass in gear and really loose some weight. Sadly I'm almost 15, 5'5, weigh about 177 lbs and I'm pretty much obese according to my doctor. :/ I wanted opinions on where ( other than my stomach which is one area I'm I'm desperate need of ) and what I could do to loose weight at the gym. Also, I feel like I have a weird arc in the back so if I loose weight would it be more profound or be less notable

https://postimg.org/image/ijovfmfdj/

https://postimg.org/image/fs6souk6j/
How much weight should I loose? What areas should I target?
8 Opinion