First, you'll need to know your target heart rate.
Target Heart Rate Range (simple)
(220 - age) * 60-90%
High intensity: ~75-90%
Medium intensity: 60~75%
(Not everyone switches over to high intensity at 75%. It's a higher percentage for those with better training.)
For power and explosiveness, work at high intensity, though it's best not to do that more than every other training session, unless you do interval training.
For faster recovery time, either is fine, though the medium intensity won't stress out your immune system like the high intensity will, hence why you shouldn't do high intensity every training session.
After your warmup, go for 20-60 minutes at your target heart rate. You need to do this for at least 4 days a week to see results. It's better to do more days than more time, when forced to choose between the two, as long as you're getting the minimum of 20 minutes in each day. If you can't put in any more days of cardio training, go ahead and increase your time, but shoot for 4 days a week.