To gain weight you will have to consume more calories from healthy foods and do some exercises.Eating a lot of junk foods and greasy foods is not the way.
The extra calories should come form healthy foods and not from junk foods containing saturated fats.Healthy fats include omega-3
essential fatty acids sources like tuna, salmon, flax, and walnuts. Good sources of protein include lean meats, fish, poultry, nuts, seeds and legumes. Healthy carbohydrate
sources include fruits, vegetables and whole grains.
You can divide your daily meals in to 6smaller balanced meals.Protein powders like protinex can be used in between meals.
Exercise is also important for healthy weight gain. Resistance training exercises such as lifting weights will help to increase your muscle size.Aerobic exercises
help for weight loss
...Above all patience is also required as it takes a while to gain weight through a healthy diet.