16 year old, need to lose weight....HELP!?

Okay so I am 16 and at school most of my friends are guys. One day my good friend Jaid turned to me one day and told me "You should join a gym." being a girl I obviously got offended. I won't lie I am 168 at the height of 5'7. I really need some help. I know about not drinking too much soda, which I seldom do, and to eat balanced but I can't seem to lose what I want to lose.