This is how I train new bodies. 10 mins roadwork 5 days a week. Raise it by a minute per week, once you get to 20 mins cut down to four days per week, 30 mins three days per week, up to 45 mins. Sounds simple but it works.
Check your resting heart rate, should come down about 1 beat per minute for the first 10 weeks.

Good luck and train hard.