Are you already running something now or starting from zero? What I'd do is start with an 8 to 10 week plan where you run 3 or 4 days a week, alternating between easier days and one or two where you bump up distance or pace. The important thing is not to go too hard at the beginning because you'll burn out quick or get injured. I started like that a while back with no race experience and it worked well for me: some days I do easy jogging, one long day on weekends where I gradually add more kilometers, and I leave rest days so your body can recover.