I would go to a dietitian in order to get some professional guidance regarding the suitable menu for you. As far as exercises go, i would start with doing a half an hour to an hour walk a few times a week (eventually you can do this every day). This way you will get some exercise and burn some fat without straining yourself too much. If you feel this is too difficult for you, you can get great suggestions from a professional physical trainer.
Remember, take it slow. See how your body reacts and act accordingly.