How can I create a child window in VST 2.4?

I create ExampleEditor.h and ExampleEditor.cpp

ExampleEditor::ExampleEditor(AudioEffect *effect)
{           
    effect->setEditor(this);
};

bool ExampleEditor::open(void *ptr)
{

    //This is it?

return true;
};

VST plugin file constructor i write

VstPlugin::VstPlugin(audioMasterCallback audioMaster) : AudioEffectX(audioMaster, 1, 1)
{
    editor = new ExampleEditor(this);
}

In what point do I need to create a window? The main window has already been created in the VST? Can I use any library or to create a window? SDL2 ? Can anyone give a very simple example?