There are two options that you can use when submitting your service metadata package to the Dashboard:
Developer mode. The package is not signed, and it must be manually downloaded and installed on every computer. Use this option if you want to save the package for offline development.
Preview mode. The package is signed and automatically downloaded from Microsoft to test computers with the appropriate registry settings configured. The package is signed by the Dashboard and runs through all the production validation checks. But preview mode does not check to ensure that the app is published to the Windows Store.