If you are "skinny" like that with no working out you will need to increase your intake of calories and protein. you could probably just add some protein shakes to your regular daily eating schedule. MAybe one between breakfast and lunch and one between lunch and supper, then one immediately after you work out assuming that you will be working out in the evening.
Do you do any sort of physical activity at all now?
If you have not been working out then you will want to follow the advice in that thread like KevinH78 said above, then after that you will want to lift with heavier weight and less reps to gain size.