if you have an idea, you should begin writing it.
dont worry, a good writer is not good by himself. he has a lot of copy editors who proof his work, and script editors who say 'this is too much' or 'we need more detail here' and an agent and publicist and a lot of other people will help you write your book in the biz.
once u write your book of at least 300 pages, print it out and start mailing it to one of the publishing houses and hope they buy it. hey a lot of great writers like stephen king were rejected up to 20 times on their first couple of books so never lose hope. also some writers have written and then had to wait 20 years for their books to be published... some of its luck you know.
dont expect to get rich quick. like anything, writing for a living is hard work.