First and foremost, weight loss is about diet... not exercise. In order to lose weight, no matter how much (or how little) you exercise, you have to work out in the kitchen!
However, given your medication, it is vital that you go speak to your doctor and get clearance and guidance on what is appropriate for you to be doing. You may even ask for a referral to a physical therapist to help you design a workout program that's appropriate for you.
Once you have that clearance and know what you're capable of, the limited mobility lifestyle center may help you out: www.sparkpeople.com/resource/lifestyle_cen