If you wanted to use Visual Studio—the premier C# and .NET development environment, the one that almost every C# developer calls home—you were out of luck. With Xamarin 2.0, that all changes.

In another step for Microsoft, the Xamarin SDK will be made open source and released on Github for all to see and use, including the Xamarin Forms library for creating quick and easy user interfaces.

Edit2: I went back to the xamarin site and noticed that when you check "I have Visual Studio" it changes the form. Should have tried before posting. Then it is just installing the SDKs for VS.

Xamarin today unveiled version 4 of its cross-platform development suite, featuring a new Xamarin Mac Agent that lets developers build iOS apps completely from within the Microsoft Visual Studio IDE.