How to start running again? 10 points!?

Okay so little over three weeks ago, I had knee surgery. Basically, i had a lateral release and dislocated kneecap. I am in physical therapy but only for 2 or 3 more weeks hopefully. Tomorrow I start running on the treadmill at therapy. Me and my sister usually run a mile a few times a week. So once Im healed and done with therapy, how can I work back up to a mile? Like how often to run and how much distance each time? Im still in pretty good shape.