Lets say that I want to be a fiction writer, how would I accomplish this?

Basically by doing what the first two have said. I personally start by writing what I've worked out without thinking down, then start planning the book from scratch. "First Draft in 30 Days" is a great book and really works if you follow and modify it for yourself. Most short stories I've written I just write from a basic outline in my head, but for full-length novels, you should plan it out, again, the way "First Draft" uses works well for me. After that, you write, and write, and edit, and proof, and edit some more. That's basically writing.