Creating an iOS app

If you’re interested in using Xamarin.Forms to target the iPhone, first become familiar with the appropriate Getting Started documents on the Xamarin website:

https://developer.xamarin.com/guides/ios/getting_started/

This will give you guidance on using the Xamarin.iOS library to develop an iPhone application in C#. All you really need to do is get to the point where you can build and deploy a simple iPhone application on either a real iPhone or the iPhone simulator.

If you’re using Visual Studio, and if everything is installed correctly, you should be able to select File > New > Project from the menu, and in the New Project dialog, from the left, select Visual C# and iOS and then Universal (which refers to targeting both iPhone and iPad), and from the template list in the center, select Blank App (iOS).

If you’re using Xamarin Studio, you should be able to select File > New > Solution from the menu, and in the New Project dialog, from the left, select iOS and then App, and from the template list in the center, select Single View App.

In either case, select a location and name for the solution. Build and deploy the skeleton application created in the project. If you’re having a problem with this, it’s not a Xamarin.Forms issue. You might want to check the Xamarin.iOS forums to see if anybody else has a similar problem:

http://forums.xamarin.com/categories/ios/

Source of Information : Creating Mobile Apps with Xamarin.Forms