To use package flighting, you must first have an existing published app. It does not have to be public, however, and package flighting will work even if your app is hidden. Once the app is live, you can create a package flight and add the package(s) intended for limited distribution in the Dev Center submission page for that app:
Your target customers must be using an updated version of Windows 10 (at least the November, 2015 update) in order to access to your packages. You also need to know the email address associated with a user’s Microsoft account in order to add them to a flight group. While users with earlier versions of Windows 10 cannot receive package flights, they will still receive regular app updates. Also, the app package in your flight can be a Windows 8.x, Windows Phone 8.x or Windows 10 package — the version restriction only applies to who can receive the package flight.
Note: Package flights can only be delivered to the following Windows 10 client builds: November 10586 and above for Desktop, February 10586.63 and above for Mobile).
Flighting is an excellent way to manage the testing of future app features, as the binaries are available to end testers quickly. Flights are published as soon as they pass certification. You can manage up to 10 different flight packages in the same app. Each flight must include the email of at least one user and can be associated with up to 10,000 email addresses.
When you are ready to promote a flight as an update to your app, just start a new submission for your app. On the packages page, you will see a dropdown allowing you to pull in the packages for your selected flight.