I know most skinny guys are like "I eat so much and I don't gain anything". It's not only how much you eat but what you eat. When I started on my diet I put on 20 pounds in 3 months, I for the longest time never thought I would put on anymore weight.
The thing is you need to eat lots of carbs, and lots of protein. Carbs are easy for your body to burn into energy, but you need a lot of it in order to make sure that your body doesn't need to use the protein for energy as well. Then when you have enough carbs all the protein you eat will go towards building muscle