I'm an author in training so i understand your situation. If you have some ideas write them down in a notebook. Bring that notebook whenever you go out and write down situations, settings or conversations that happen. As for starting the story, it's a good idea to either start it off with a prologue about the past of a character, someone talking, or even describing someones feelings. For Example: 'The hardwood floor creaked as i trudged down the stairs, drawing closer and closer the the darkness' And for publishing you can either self publish or go to your local book store for help.
Notes, notes, notes! Just write, darlin'! You will piece those notes together eventually. You're getting ahead of yourself - baby steps! Nobody just writes a book. NOTHING happens overnight! Baby steps ...... Nobody ever wrote a book in under 2 years! You need 2-4 years if this is your first attempt. DON'T GET DISCOURAGED!