I'm 25 years old. My hight is 5.8 inch and my weight is 50 kg. now I cange my body and muscle or gain weight quickly with out any medicine , so how can do it.

Eat more and lift weights.

Yes, it's that simple, but it's not easy. You must eat more calories or you can't gain weight, and lifting weights (heavy enough to cause you to struggle) will help you put on muscle rather than fat.

To gain weight and be healthy you need to consume more calories than you burn them every day from healthy, protein enriched, and nutritious foods and choose the right types of exercise.
Exercise a little like mild weightlifting so as to feel hungry, to eat more balanced food and to develop muscle.

That's not easy matter, you have to drink more water and don't be hot... lift the dumb bells heavily... surely your muscles should asked protein.. that time you have eat the any protein food like beef, badam , milk etc...