Depends on your age.
How big you will get depends on testosterone levels. The higher the more it grows. For example. Boys with micropenia (very small penis) are treated by putting testosterone cream on the penis or by injections. Do not do this without a doctor. The best thing is to eat healthy. Fruit and veggies. Pumpkin seed and Pistachios as well as other things raise testosterone levels.
Easy on the sweets. No smoking! How big you get pepends on how big your father and your mothers father is. That is the genetics that controls how high your testosterone level will get.