I'm now 18 and i want to grow up my height more so what to do.

Familial trait: An 18 yr old is not growing taller if his growth plates have fused. If not fused, he will grow a little bit (pediatrician's growth chart for him can tell if growth has stopped). To look taller, one can choose properly designed clothing & shoes, and have good posture. Vitamins, supplements, "special" foods, exercise, etc... will not make a person living in the U.S. taller (height here is genetic).