TL;DR - Yes you can use NuGet packages/.NET Libraries.
The game assemblies are just .NET. By default each game Solution has a core game project/assembly i.e.
MyGame.Game and 1 or more platform specific project/assembly i.e.
MyGame.Windows. By default the core game assembly is .NET Standard 1.4. (If you only plan to target Windows desktop, you could change this to target the Full .NET Framework if you prefer.) Each of the platform specific assembly/projects differ. For example:
- Windows platform assembly is .NET Framework (mine seem to be 4.6.1).
- iOS and Android platforms use Xamarin.
- Linux platform uses .NET Core./Mono
See platform docs: http://doc.xenko.com/latest/en/manual/platforms/index.html
Hope that Helps.