Everyone has an idea for a story. To dream up ideas is a part of being human. Writing down an idea is what changes you from being a dreamer to being a writer. When an idea is unwritten it is half-real like a dream. Writing it down is the act of creation. Writing is making something out of nothing.
Once you have your idea on paper it might need to be worked on. It might need to be changed and developed or revised. All those things are secondary because the most important and first step has been taken. You have written something down.
So take the plunge, write down your idea! Becoming a writer is easier than you think.
Can you name the original X-Men? Do you know who the first members of the Uncanny X-Men (the second team) were and how many are still in the group? All right, how about the Reavers? Or the New Mutants? What about Generation X?
My point being that as a reader, anyone who followed the far-ranging cast of characters created by Stan Lee and Jack Kirby in the 1960s taken by Chris Claremont in the late 70s and expanded beyond any scope or definition of Reason into the 90s had to have an inclination toward keeping literally hundreds of mutants straight. Fortunately there were visual cues. Unfortunately, not every artist interpreted those visual cues the same way.
But there was a lesson there for young Jason as he aspired to his own dreams of writing. (Sorry, the Claremont pretentiousness sometimes slips over the levee. <cringe>) The lesson was that for a reader to enjoy a story with an enormous cast, the author had to have a kind of shorthand that immediately cued the reader. Sometimes it’s the way a character talks, or a catchword or phrase. Or maybe it’s patois that’s stylistically disguised as “accent” ala having an English character say “Eh, wot?” That’s all in the writing.