How can i, a 16 yrs old boy standing 5'10", weighing 54 kg(120 lbs) gain weight?

I have tried hard but not able to gain weight. I do plenty of exercise, eat a lot. But no results at all.. Due to exercise, my body has become pretty muscular but no significant weight gain. I want have at least 60 kgs (132 lbs) on my body.. Plz help