Hlw sir/madam am 21 years old. my height is 4.9ft. how to increage my height?

Hard to say: An initial approach would include an x-ray of your wrist/hand to identify your growth centers. If they suggest a bone maturity more like a 12 yo you need an evaluation of your growth hormones. If more like 18 or older, your growth centers have closed & you are unlikely to grow taller. Good nutrition, sleep and good health support normal growth.

Not much: Can be done other than wearing platform shoes.