A Walking Program
Embark on a walking program. For four days a week, walk 30 minutes. Do not use a treadmill—go outside. Yes, outdoors. Part of rehab for couch potatoes is getting outside.
If you are physically unable to walk 30 minutes, walk 15 minutes. If you cannot do that, go to your doctor and ask if you are fit enough to start exercising. Even if you just do 5 minutes a day, start.