You are a new rider trying to get into shape, keep it simple. Forget meters and formulas, ask yourself how you feel. If you feel tired and sore after a training ride but recover completely within a day or two, all is good. If you feel severe point pain, have any disability, or feel weak, ill, and poorly motivated for days you are pushing too hard. Your level of effort should be challenging but not overwhelming. When on a training ride I like to push a pace where I can speak in short sentences and am breating hard but smooth and evenly. If you are gasping for breath or feel light headed, back off a bit.
Many fine athletes trained for centuries without the benefits of poser meters, heart rate monitors, Strava and Garmin. Don't get me wrong, they are fine tools, but the key is to learn to listen to your body, monitor your results and then make the necessary adjustments. All the other tools just put numbers to what you should already know (and maybe provide some motivation).