How would you use a Xamarin Component in Xamarin Forms?

I am trying to implement the Signature Pad Xamarin Component in a Xamarin Forms Solution and have implemented a signature activity for Android and UIViewController for iOS. Then in my forms I have:

#if __ANDROID__
Forms.Context.StartActivity(typeof(proofsafe.Android.signature));
#endif

What is the equivalent for doing such a thing with a UIViewController for iOS?