Being an actual author isn't a walk in the park. realistically, if you're not writing right this second, as in, you stopped writing to read this, so you're not, then you're doing it wrong.
if that makes any sense.
authors are almost constantly writing. It's a trained skill, and like any other trained skill, to become masterful at it, takes many many many many hours of practice.
If you want actual advice, don't start with a novel sized story. Challenge yourself to write 10 short stories, all with actual plots, beginning, middle, end, conclusion, conflict, overcoming that conflict, all that stuff. 5000-6000 words. You'll learn more about actual story structure making small stories then putting all of your work into a 80,000 word novel which might never actually get finished.
So in short, my advice is to get good at actually telling a story before becoming a "novelist". And novels are bitches to write, let me tell you, I put about 30,000 words and a year of my life into trying to make one. it's tough work. At 15, if you have the drive to do anything close to that, then you're much better then me.
edit: read some of the stuff in the post above mine, and I have to give you another little tip - never use a large word when a diminuitive one would suffice (badoomtish). Unless you're trying to boost your story's graded reading level for some unearthly reason, there's not so much use in using large words when you don't need to. *rechecks* ehh, maybe it's just first impressions.. your first sentence is ungainly and sort of throws the whole thing out of wack. I'm not even sure if it's an actual sentence actually. don't really care enough to sit down and ponder it, sorry. It might be.