Ordinarily, young men have not reached their adult height at age 15; and it isn't unusual for them to grow another inch or two between their late teens and very early twenties. That would seem to indicate that you may be going to grow a little more in the next couple of years. In fact, the human skeleton does grow until about 20 years old.
This link summarizes the different ways people can increase height. These methods may not be right for you (or for any number of other people who would like to be taller). Ordinarily, some of these extreme steps are not for the "average person who just isn't as tall as he'd like to be".
I know everyone has his idea of how tall he'd like to be (or how much shorter me may wish he were - that happens too). Sometimes we need to be ok with what we happen to end up being. Even it isn't your preference, it's not a terrible thing to be average height or short (not even for men). My father was a short man, and he was attractive and masculine (and all my girlfriends' mothers thought was "so handsome"; so did a lot of other people).
It may not answer your question the way you want, but I think you should aim to eat a healthy, well balanced, diet with lots of nutrition. If you have more growing to do your body will need the healthy, complete, diet to support that growing. Get plenty of exercise because exercise helps bodies do whatever they need to do better. It may seem silly, but get enough sleep. Not getting enough sleep can take a real toll on health, and a potentially "growing young man" needs enough sleep. In other words, take care of yourself in order to give any growing the best chance it can have. :)
If you're extremely short now it isn't likely you'll grow to be extremely tall in the next two years, but you may reach average. If you're average, you may grow another couple of inches. Try not to emphasize the importance of height too much, because it really it isn't all that important.