See create-react-native-app:

$ npm install -g create-react-native-app
$ create-react-native-app my-app    # on Windows: %appdata%\npm\create-react-native-app my-app
$ cd my-app/

Install extra dependencies:

$ npm install --save-dev chokidar-cli@1.2.0
$ npm install --save-dev elm@~0.18.0         # FIXME: how to make it add version "~0.18.0"?

Add the following lines to your package.json, in section "scripts":

"watch-elm": "chokidar \"src/**/*.elm\" -c \"npm run build\" --initial",
"build": "elm-make src/Main.elm --output=elm.js",

TODO: to be continued...