Never mind, figured it out on my own thanks to solution in another thread:
@int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
QQuickView view;
view.setSource(QUrl::fromLocalFile("qml/GUIManager/main.qml"));
QQuickItem *mainStage = view.rootObject();
QQmlComponent blackRectComponent(view.engine(), QUrl::fromLocalFile("qml/GUIManager/BlackRectangle.qml"));
QObject *blackRectObject = blackRectComponent.create();
QQuickItem *blackRectItem = qobject_cast<QQuickItem*>(blackRectObject);
blackRectItem->setParentItem(mainStage);
view.show();
return app.exec();
}@
http://qt-project.org/forums/viewthread/31318/