I'm 6 feet but my weight id just 59kg how can i gain weight?

Kcal in > kcal out: To gain weight, you must consume more calories than you expend in activity. I'd talk with a nutritionist - they can help guide you to healthy sources of calories like lean meats, good fats, etc. There's no trick to gaining weight, no simple pill or guaranteed diet, and genetics can make it hard to move above a baseline weight. But it really comes down to eating more calories than you burn.