To start the server, simply run python server.py.
Then point your browser to localhost:5000.
You need to have a working python installation, with the package Flask installed.
If Flask is not installed, run pip install Flask.
Do you want to change the css? Edit files in the static/less folder.
Then, to compile "less" files into "css" files, run grunt less or run grunt watch to have it done each file save in the background.
If you use Heroku as the production server, follow https://devcenter.heroku.com/articles/getting-started-with-python