Eat less move more. Simple concept.
The saying is "Abs are made in the kitchen" which is quite true since abs are not exactly buildable muscles like arms and legs are. The abs are a connection point for the muscles, hence why they are shaped the way they are. The best way to look larger and more muscular is to lose body fat; the only real way to lower body fat is to eat right (unless your a gelatinous blob in which case just moving will help you lose body fat).