essentially, you need to eat more calories than you burn.
and to put on muscle, you need to work out.
protein shakes are great, i used to date a guy who was obsessive on his weight and would weigh himself multiple times a day -> don't do that.. it is silly.
weigh yourself once a week, it will be much more accurate.
what works for somebody else won't necessarily work for you.
ultimately, your metabolism will eventually slow down.. don't stress about being skinny you'll be wishing for it in 10 years time.