System.IO.IsolatedStorage

I am creating PCL in Visual Studio 2013 targetting following frameworks .Net Framework 4.5 or Higher WP8 Xamarin Anroid Xamarin iOS

As told in http://docs.xamarin.com/guides/cross-platform/application_fundamentals/building_cross_platform_applications/part_5_-_practical_code_sharing_strategies/

documentation,I can use these libraries from Windows platform. I have used same functions,classes and libraries which are designed for Windows platform. But whenever I am trying to insert a statement using System.IO.IsolatedStorage;

It is giving error that line. I can't insert these packeges in my PCL project.How can I overcome this? Same problem is coming for xamarin studio also.