Chances are the only way to eliminate that extra skin is to have it removed. But it depends on how long you were heavy, your age and the elasticity of your skin. Working out won't tighten your skin. It might fill it out a bit with muscle but I am sure that the areas you are most concerned about are your waist, hips and thighs.
Congratulations on losing weight! It's a tough road and you're making it!