Couch to 5K is a 9 week programme designed to get you from the couch to running 5k (roughly 3 miles). The plan involves 3 runs a week, with a day of rest in between, and a different schedule for each of the 9 weeks.
You can find more information about the programme and more advice on the NHS website: www.nhs.uk/live-well/exercise/get-running-with-couch-to-5k/#what-is-couch-to-5k