Youll have to write it yourself, a good idea for a story is something but actually writing the thing is something very different, mostly because the idea you have in your mind as it is will only give you a few pages right away, youll have to develop dialogues, maybe create new characters/personality traits, describe scenarios, among other things you havent thought about it yet(at least not thoroughly I imagine).
No one is born a writer(the talent might be there but at a raw form in the beginning), but creativity is more of a personality feature, so if you have it you can start writing. Dont mind grammar errors and such, after you write a bit ask someone who has a good understanding of the language to point out some of the mistakes. Youll get better eventually.