The most important thing is to give your body enough time to adapt. New muscles and tendons that have not received any kind of stimulation for a long time will need to adjust to the new more physiologic and natural way of walking or running. You must listen to your body: if you feel any pain while running or walking fast, stop immediately. The bones, ligaments and tendons normally need time to adapt.
If you are diabetic, the foot sensation might be lost so you need to be very careful.
Start by walking for 5-10 minutes for the first two weeks. Gradually increase the time, but listening your body. Try running a short distance and gradually increasing it. If you want to run, Feelmax shoes are perfect for a number of activities, both indoors and outdoors.