I want to bind the OnVirtualKeyboardShown delegate and use it. How do I bind?

yeah you should get the delegate first so you can bind function to it.
here is the example:

// yourClass.h

#include"GenericPlatform/GenericApplication.h"

// create a func to bind
void FunctionToBind();

// yourClass.cpp
// find a place to put this code in , such as the construct function
// get the singleton
TSharedPtr<GenericApplication> App = FSlateApplication::Get().GetPlatformApplication();
// get the delegate
if (App != nullptr && App.IsValid()){
    App -> OnVirtualKeyboardShown().AddUObject(this, <FunctionToBind>);
}

That’s All. I use this function in PE-Game so i can know when the keyboard come out.