Drive down to Hollywood with a hundred copies of your script, give one to every director you can find, and write them threatening letters until they accept it.
But yeah, pretty much anyone can write a script. If you can somehow come into contact with someone who has influence in the movie world, get them to read your script, and get them to LIKE it-- to say, 'wow, this is original and really good'-- then you just have to hand it over to them and let them take care of it.
Or get it done independantly. The most important first step either way is to find someone with influence. Who can fund your project, find you the crew you need, and get the film made. That's what comes first.
Well, after writing the actual SCRIPT, that is.
Why So Green And Lonely? We Are Accidents Waiting To Happen.