Xamarin.Facebook from nuget in Shared Project

Hi
I am trying to reference the xamarin.facebook from nuget.but i am getting error while installing.
Installing 'Xamarin.Facebook 4.1.0.0'.
Successfully installed 'Xamarin.Facebook 4.1.0.0'.
Adding 'Xamarin.Facebook 4.1.0.0' to SampleApp.
Uninstalling 'Xamarin.Facebook 4.1.0.0'.
Successfully uninstalled 'Xamarin.Facebook 4.1.0.0'.
Install failed. Rolling back...
Could not install package 'Xamarin.Facebook 4.1.0.0'. You are trying to install this package into a project that targets 'portable-net45+win+wp80+MonoAndroid10+xamarinios10+MonoTouch10', but the package does not contain any assembly references or content files that are compatible with that framework. For more information, contact the package author.

Please can anyone help me out.