Note that the Fenix does not use the default MSFS database, so you want to also update the Fenix database itself. This is done in the second tab (Microsoft Flight Simulator — Installed Outside Simulator on the left, below the main tab).
Updating the default MSFS database will give you updated data in all default aircraft as well as many third party aircraft that use said database as well (in addition to keeping everything in sync between the Fenix and the rest of the sim, including updated navaids etc. as Richard already mentioned).
Note that while the built-in MSFS Flight Planner will auto-populate the flight plan in some default aircraft’s avionics, this will not work in the Fenix (this would not be realistic way of doing it for real pilots). Instead, you can use the Fenix’s Simbrief integration to import a flight plan via “INIT REQUEST” in the MCDU:
Note that the place where you enter your simbrief id has changed in the latest version of the Fenix (was in the Fenix standalone app, is now done via the EFB or the MCDU instead); oddly I could not find an up to date video in 
so here’s one in 
:
If you want to use the built-in MSFS air traffic control, you can import your simbrief flight plan into the sim’s flight planner using a .pln file:
Regards,
Tim