An excersize bike is considered more of an endurance for training. But yet, it does help the leg muscles a bit.
Try setting it to high, to the point where you have to pedal harder. It works the thighs.
Also, try doing squats for your legs. Crunches would do great for your abs.
Dont forget to intake alot of water when working out. Water is like a fuel to your muscles wich causes them to grow.