How do i gain weight fast...any please provide me the best vitamin that i can gain weight fast?

Add healthy food: To gain weight you have to consume more calories than you are burning. Do this in a healthy way though. Don't choose junk or fast food. Keep a well balanced diet and make sure you are getting all the nutrients you need. Weight lifting and other muscle building exercises can help you increase your body mass. To my knowledge, vitamins won't help at all.