How does anyone become good at anything? Practice, practice, practice, if you train hard every day, you will play NRL.
I'm 15 at the present, I've met a few NRL players while playing for rep teams up in Queensland. I've always been told no matter what position you play, fitness is the first key factor, Mindset would be the second and strength would be last. Improve all of these in your training and you can go far.
Can you drink yourself senseless, take illicit drugs, have a punt, drive without a license? Your in!!