the type of food, at what time, and for how long?
Lots and Lots of protein before and after working out.
after working out have chocolate milk
depends on what kind of body you want to build. A dozen donuts every morning will pack on the weight. A 6 pack every afternoon will give you a different kind of 6 pack.
Your regular diet plus a few more calories in carbohydrates, lots of extra proteins, and "good" fats. For how long? For about as long as you're going to be trying to build mass. That could be weeks, months, or years depending on your goals. If you're working out at a gym, talk to one of the trainers. They'll usually be able to give you some detailed diet advice. I don't recommend them myself, but they may also suggest a supplement or two to help you along. Even if you're not working out at a gym, it might be a good idea to call a trainer for a few sessions every now and then to get you started. You should never embark on a bodybuilding mission without some kind of professional guide. If you're also trying to loose body fat, have diabetes, have a dietary problem, are vegetarian/vegan, or even if you're just looking to eat healthier... see a dietitian.