Start by walking, first. Every day for a set amount of time (say, 10-15 min) go outside and walk around the block or a nature trail or anywhere, as long as you’re moving. Gradually start picking up the pace & adding more time to your outings. Soon you’ll be running! But don’t rush it! If your body isn’t usually very active, it may take a month or two for it to get used to the exercise. Keep at it! ;]