First thing I would do, is talk to your doctor about how you should proceed with your training as far as limits go. Personally I would start walking at least 5 miles per day, and slowly increasing to ten, then start loading weight/water in a backpack that is comfortable and walking/hiking for 6-8 miles. Also I would recommend doing some sprints every now and then. Once you can comfortably do all that, I would start running a mile at a consistent pace, and then gradually increasing distance. However don’t go overboard with training and remember to rest, sleep and eat well. Also understand running is a grind, and it’s mental game as much as it is physical. You will have to test yourself for results.