I am 19 years old.my height is 182cm and weight is 59 kgs.i am very lean since childhood.how can i increase my body?what food i had to take?

Protein: You are slightly underweight. Since more and more people are overweight or obese, you may think that your are severely malnourished. If you want to gain lean muscle mass, increasing your protein intake would help.

Eat healthy foods: high in calories. Eat 6 meals /day. Work on strength training to build large muscle groups. Work out w heavier weights w fewer repetitions. Sleep at least 8 - 9 hrs/night. Hydrate well w water. Foods to help w weight gain: almonds, cashews, pecans, sunflower seeds, flax seeds, walnuts, hummus, avocados, granola, trail mix, dried fruits, protein shakes & bars, lean meats, poultry, fish, smoothies