Start lifting weights at least 3 X a week and eat a good balanced diet. No Junk food. Eat 6 small meals a day with a low fat protein at each meal.
With a weight like that you don't need to do a lot of cardiovascular exercises, mainly a lot of weighttraining. You might want to get some help at first from a personal trainer to become familiar with the exercises and how to maintain good form at all times, so you won't hurt yourself.
Good Luck!