How does a writer become a writer?
First, comes a love of stories. Combine that with an imagination, a child who is often alone, and the availability of books (lots of books) and the result may very well be a future storyteller.
I learned to read in Kindergarten, and by the time I was in the second grade I was reading everything I could get my hands on, including Readers Digest and National Geographic magazines. My father's extensive library was all open to me, from Shakespeare and the Classics, to hard-boiled mysteries and romance, tales of Tarzan and high sea adventures, Ian Fleming and Agatha Christie, Lovecraft and Poe. I wrote my first short-stories in the second grade.
If you have a love of stories, and want to try your hand at writing some, abundant resources exist. Magazines like Writers Digest and Poets and Writers are a must. Join an organization. Many local and regional organizations exist. Attend writing conferences to meet others who have your same writing interest. Take a creative writing class, and get active in a book club or library.
Writing takes a lot of work, and a lot of tenacity. The literary world is full of writers who have spent decades perfecting the craft of writing - who suddenly become an 'overnight' success.
Don't delay. Get started, and keep going. Your writing is an insight into your soul. Share it with the world.