In order to pack on some muscle weight you need to go to the gym and focus on training heavy with free-weight exercises: squats, bench press, dead lifts, shoulder presses, dips, incline presses, barbell curls, dumbell rows, pull ups, etc. Secondly, boost the HEALTHY FAT in you diet. Namely, monounsaturated fat. Simply, go to the store and buy a bottle of olive oil. It is good to cook with and goes great on salads and whole wheat pasta. Why boost the fat intake? It adds calories and, most importantly, it boosts your testosterone levels. Studies have shown that both monounsaturated and saturated fat boost T-levels. Unfortunately, too much saturated fat raises your LDL cholesterol and clogs your arteries. However, monounsaturated fat is healthy and actually lowers LDL and boosts HDL. Finally, supplement with creatine. It will add 5 pounds of muscle within a week. You can buy creatine at Wal-Mart.