Before you start to write, you will need to create an outline for your book. This will prevent you from getting writer's block.
If you discipline yourself to write something daily, no matter how small, you will make progress with your book. Do not go back and edit. You can rewrite later.
This is necessary, since most major publishers will not accept unsolicited manuscripts.
In order to sell your book, you need to find a publisher who specializes in the type of book you are writing.
Even the best writers need the help of an editor. Often they can spot errors that you missed and make your work better.
Rewrites are a chance to improve your work--most writers rewrite more than they originally wrote.
The time required for publishing a novel is about two years.