aim for 2-2.5 pounds of growth a month which is about half a pound a week
so eat around 200-350 calories more than you burn everyday
eat often, eat healthy, eat a very wide range of foods, lots of protein (150-250 grams), make sure to eat before bed and after waking up, lots of fruits + veggies, some good fats (peanut butter, nuts, etc...)
that's the basics - come to bodybuilding.com - they got a great teenage section to help n00bs step by step
great board in general (you can discuss your workouts, how to improve your workout/diet, or just fuck around in the hilarious misc section)