One of the first things you need to decide when you start writing any kind of story is whose viewpoint you'll tell the story from, and in what voice. Will you tell it entirely from the viewpoint of your protagonist (hero)? Will you switch among different viewpoints, or use an omniscient (all-knowing) narrator who can tell the reader things that the characters themselves may not know? Will you write in the first person I or the third person he and she?

Let's start with the last question - which person - first. There are no set rules to the question; you must be guided by your own preference, and by your sense of your story's needs. Many people find it easier to write successfully in the third person. Although most of us are familiar enough with first person - we write letters that way, and diaries - it may be that it is more difficult to write first person well, in a way that brings your story to life interestingly for your readers. Experiment and see what feels right to you. If you're undecided, you might be better off starting with the third person.