Study, study, study. You can be assured that, that kind of role is not acquired over night. It is something that always comes from hard work, good work, and perseverance.
When you get to years 11 and 12, take on more English classes, and perhaps any subjects that you could see yourself writing about. Because to be an editor, you need to have a head full of knowledge and experience.
Then when you get to uni, take up a degree in journalism, and maybe even a creative writing to help expand and sharpen your skills.
In the mean time, I would suggest honing your skills by yourself; write some articles for magazines you think you may want to work for. You don't have to send them in, just do them for practice.
All in all, just keep writing like a madwoman, with the end goal of being an editor always in sight.
Good luck to you, and like I said, no one becomes an editor over night... unless you start a magazine/online news site/ newspaper. But that is a whole different kettle of fish.
Hope i've helped.