It can be challenging to get all the pieces together for Xamarin (Forms) to work. Here’s some guidance on how to get past those first hurdles.
Install Xamarin for Visual Studio
From Visual Studio 2015 Xamarin is included with the installer under Cross-Platform, but you can always use the standalone installer from Xamarin’s web site.
Follow the steps of the installer to get going. This will add “Xamarin Visual Studio” integration and project / file templates for Xamarin Droid | iOS | Forms projects.