My age is 18.i am thin.what is the best way to gain weight without going to gym.what should i eat..my weight is only 50kg?

Body Weight Exercise: To gain weight in a healthy manner you need to exercise with progressive resistance to build muscle. It's a bit slower without weights, but can be done-hindu squats, hindu push-ups, pull-ups. Can try kettlebells. Eat lots oflean protein-fish, chicken, turkey. Eat fruits/veggies. Avoid processed carbs-eat complex carbs. Genetics will play a role in how much weight you can gain.