Are you sure you are very skinny? I am 183cm and is 70kg, but I
don't feel like I'm stick-thin. By the way, your BMI in healthy
range 
If you wanna be "bigger"...have more protein in your diet. Eat more
fish, chicken and lean meat. Cut down on carbohydrates like rice,
bread and noodles. Otherwise, you might want to opt for supplements
like protein shakes and weight gainers. Go to gym religiously to
build up mass.
Having a better physique boosts self-confidence, but being healthy
mor important.
