how to include one widget in another?

[aurora]

I created two widget one by command another by Qt form designer. The code as shown below. When i execute two separates forms displays....What changes do i need to do, so that one form displays inside another form as single widget?

fileopen.cpp

fileopen::fileopen(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::fileopen),
    m_layout( new QVBoxLayout() )
{
 
    QPushButton* add = new QPushButton("Add");
 
    connect(add, SIGNAL(clicked()), this, SLOT(addRow()));
 
  m_layout->addWidget(add);
    m_layout->setAlignment(Qt::AlignTop);
 
    QWidget* w = new QWidget();
    w->setLayout(m_layout);
 w->show();
 
    ui->setupUi(this);
 
}

fileopen::fileopen(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::fileopen),
    m_layout( new QVBoxLayout() )
{

    QPushButton* add = new QPushButton("Add");

    connect(add, SIGNAL(clicked()), this, SLOT(addRow()));

  m_layout->addWidget(add);
    m_layout->setAlignment(Qt::AlignTop);

    QWidget* w = new QWidget();
    w->setLayout(m_layout);
 w->show();

    ui->setupUi(this);

}

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