gain weight

I am 22, 5'1, 83 pounds. I cant gain for sh*t. I'm done feeling like a twig, which I am. I'm done getting comments about how I don't eat and how many burgers too shove down my throat. I've been trying to gain for so long but no matter how much I eat its IMPOSSIBLE. I can eat all the fast food in the world and still be in the 80s. my question is where should I even begin???? what should I eat//drink to gain weight??? I feel like everything I try im just doing it wrong to be in this weight still. it's been 2 years being 80 something pounds. all my weight goes to my stomach I want to gain all around😞🙁 please please help🙁🙁🙁🙁