I used to be skinny too. Well about 5 years ago, I was 165cm and 50 kg. But i went overseas study, after about 2 years I was 167cm and 60kg (roughly estimated).

My main advice is do not skip any meals, be it breakfast/lunch/dinner/supper. Yea rite, supper is a must to gain weight.

If you are in a gym session, of coz they wont advise you to take those fatty stuff and take high protein product, but hey you dont have anything to shape your body apart from bones. So gain some meat first, before you hit the gym.

Usually for skinny ppl i discover, it's either they skip meals (i used to skip breakfast alot, and lunch) or their metabolism is too high compared to what type of food or the amount you eat.

So if a normal person should consume around 2000 calories a day, you should have like 3000. My fren used to tell me he bcame fat by eating burger for supper. Eat more high carbo and protein stuff.

For exercise, the basic but useful one is push-ups.