what should i do to gain weight?

My height is5’4" around and my weight is not even 30kgs! I am very very thin since i am in 12th std and i have to compete and join a medical govt collage but physically i am not fit at all.i want to look normal…even a 1.5year old baby’s face is larger than mine!1year old baby has more muscles than i have…please provide me some instant solutions…i have tried almost everything but nothing happened.i am also an anxietic…and because of it i am afraid of peoples and crowd and any kind of test.i not able to eat anything before my tests are over,even if the ecam is in the aftrnoon.i am afraid how will i give my boarfs and competitions.before exams or any where in between people i have a vomitting habit and it is since years…before every exam it is very hard to handle.if i eat anything i will surely vomit and if i dont eat anything than chances are there that i wont vomit…waiting for the solutions since years…

Ensure protein drinks will make you gain weight. I was on them due to being very thin and gained weight without any extra effort other than normal exercise and physical therapy.