Tapping the Right Stick will cause you to dribble.While moving toward the basket, move the Right Stick in any direction to dunk.This activates your character's turbo sprint and modifies both the shot button (Square on the PS4 or X on the Xbox One) and Shot Stick.
Using the Left Stick, move your player toward the basket.
2K revealed that one of the common question gamers asked them was on how to dunk in NBA 2K16.