Yes, lifting weights will help with body composition. At your age, you should be able to build muscle very quickly if you put in a little effort. If you can keep it up for six months, people will start making comments about your improved physique. If you can keep it up for a year, and work hard the whole time, you will be a beast.
Get a gym membership and keep it simple. Learn a few compound lifts–for example, bench press, overhead press, squats, dead lifts, and pull-ups (or lat pull-downs)–and that will be enough to start. You might try a 3×5 or 5×5 program first.