hi, rather large bodybuilder here of 22 yrs experience.
light weights do not build big muscles, big weights = big muscles
not that easy though obviously, you also need a high calorie, high protein, low fat diet broke down into 6 to 8 meals a day to provide the muscles with a constant supply of protein for growth.
rest is also very important, both resting in between workouts and a good 8 rs of sleep a night to allow your body to repair and recover.
when training heavy its essential that you warm up thoroughly to help avoid injury, that you do not over-train as well. your workouts should be short (1 hr max, 4 to 5 times a week) but very intensive. larger body parts such as chest, back, legs, delts need more exercises and sets than the smaller ones such as biceps, triceps, traps.
buy yourself a couple of bodybuilding mags such as flex and learn from then or try a personal trainer just for 1 or 2 sessions.