So, you have The Story.
Now you just need to write the damn thing.
Here are some tools that I have found very helpful in this process.
1 - An extensive library. You've all heard it before, from any number of successful writers. If you want to write, you need to read. A lot. The reason you keep hearing it is because it's true. Nothing will make you more aware of how to do it than to experience it at somebody else's hand. Writing is one of the rare activities where practice does not make perfect. Unless you read somebody else's work, you'll never get better with your own. Just try to make sure that what you're reading is not close in style/theme to what you're writing. You'll copy it whether you intend to or not.
2 - Paper. And lots of it. I don't care that you're writing this on your laptop. You could be scribbling it with charcoal on the walls of your bedroom. Doesn't matter. You will need notepaper, and a lot of it. I use a Moleskine notebook for mine, and carry it with me everywhere. There are three pens tucked into it, and it is wrapped in an elastic. It doubles as a carrying case for essentials (smokes, lighter, pens, bus pass, etc...), but it's primary function is to write down ideas wherever they come to me. I have two books almost completely laid out in that Moleskine, and the bare bones of several others. Snippets of dialogue that I don't even know where they'll go, scenes that popped into my head and could be useful down the road, all sorts of things. Always, always, always have notepaper with you, and something to write with.
3 - Privacy. If you have a spare bedroom in your house, convert it to an office. Get a desk, some bookshelves, and set it up as your writing room. Let everybody else know that when the door to that room is closed, the only reason to interrupt you is imminent death. Get a lock on the door if you can, but stress that no one should be knocking on that door unless it is a dire emergency. There is nothing worse than being in a groove, with words flowing out of you in a torrent, only to have your concentration broken by a knock on the door, or someone barging into the room. People who do that should be shot, in my opinion. There is no going back to it, you've lost the moment, and there is no way to get it back.
That's pretty much it. Personally, I use a lot of music, as well, but that's just because I'm a huge audiophile. Some people like silence when they work, and that's fine too. I get bored when it's quiet, though. As well, I need a squeaky chair. Not for the noise, not really. It's weird, but if I lean back in my chair to take a breather, and I don't hear the squeak, it throws me completely off my game.