First and foremost, you want to follow your doctor's orders. Take your medication as directed and follow a sensible eating plan. Your doctor may have you seek advice from a Registered Dietician.
You will also want to follow a regular exercise plan. In order to lose weight, you need to burn more calories than you consume in a day, so you need to be moving. If you have not exercised recently, or most of your life, you will want to start out slowly. Walking is a great form of exercise. If you take 10,000 steps per day, you will be burning approximately 400 calories just by taking those steps. Walking is a great stress reducer, good for your heart, bone density, and overall health.
You will want to incorporate resistance training as well. By increasing your lean muscle mass (LMM) and reducing your percentage of body fat, you not only become healthier, but you burn more calories even at rest. For every pound of LMM you put on, you increase your burn rate by approximately 100 calories while at rest. Just think what that can do for you overall!