Reiterating what Lord Harris said —
Bone Pressed = measuring from the top of your penis, press the end of the ruler against your pubic bone. BPEL is a “scientific” measurement — its purpose is to eliminate the variable of your fat pad, thereby measuring penis only. That way you can track the results of your PE program, modifying as needed.
Since BPEL is for tracking, the only thing you really have to worry about is doing it consistently — the same way every time you measure.
Non Bone Pressed = to me that is a worthless measurement in terms of PE. It only tells you about your fat pad. And your fat pad can vary on a daily basis. Sometimes mine is 1/3 of an inch. Some times it is a 1/2 an inch. It can vary depending on how much water you drank, how many salty snacks you ate, is it hot out, etc.
In a way NBPEL is the measurement you would tell somebody in the “real world” if you were telling people the size of your penis. Personally that topic never comes up in my conversations!
Guys have different ways of measuring NBPEL. Some from the top like BPEL, only not pressing the ruler in.
Others have a different approach to it. Tazbonito measures his NBPEL from the side. Stand in front of a mirror and turn to the side. Measure your visible penis with the ruler from the side. I think there is something to this approach, as that is the viewpoint that a new sexual partner will have. She will most likely see you from the front, side, or bottom initially. Seldom are you seen first from the top.
Routine - maybe the standard Thundersplace newbie routine is too much for you. Some guys (like me) do better with something lighter. Take a look at this newbie routine. I did something similar when I first started:
NEW newbie + advanced routine