Xamarin provides tooling for both Xamarin Studio and Visual Studio to automate the migration process from the Classic API to the Unified API or you can convert the project files manually.
While the using the automatic tooling is highly suggested, this article will cover both methods.
Any component that you have included in your application will also need to be updated to the Unified API or you will get a conflict when you try to compile.
For any included component, replace the current version with a new version from the Xamarin Component Store that supports the Unified API and do a clean build.
To see what updates are available, or to install a software update from the Terminal of OS X, you’ll use the ‘softwareupdate’ command as we’ll instruct below.