It's pretty simple. Stop eating so much, and start exercising more. It wouldn't be wise to go RUNNING at your weight, but you need to start BURNING more calories than you take in. Eat low fat / high protein / low carb meals WITHOUT FAIL, and get used to NOT eating cakes, ice cream, ho-hos, etc. Those foods don't do you ANY good.
Good luck! You have your work cut out for you.