There is no license sharing on Microsoft Flight Simulator. When using Family Sharing, the additional content and online features are only available for the account that purchased the sim.
Each Microsoft Flight Simulator user needs to download the app on their own windows profile and log in to their own Microsoft account/gamertag. You'll find more information about app & games sharing here: Sharing Windows 10 Store Apps with your Family
Content purchased on the Marketplace is not shared with other profiles using the same console.
Discover how to authorize shared computers and users here: Steam Family Sharing