Qt Call function in main class from qlabel click event

I have a main class like this

class ImagePuzzle : public QMainWindow
{
    Q_OBJECT
public:
    ImagePuzzle(QWidget *parent = nullptr);
    ~ImagePuzzle();

private:
    QVector<QVector<ClickableLabel*> > imageLabelArray;
};

In order to create a click event for the labels I followed this doc: https://wiki.qt.io/Clickable_QLabel and make a class like this:

class ClickableLabel : public QLabel {
    Q_OBJECT

public:
    explicit ClickableLabel(QWidget* parent = Q_NULLPTR, Qt::WindowFlags f = Qt::WindowFlags());
    ~ClickableLabel();
    void setId (int id);

signals:
    void clicked();

protected:
    void mousePressEvent(QMouseEvent* event);

private:
    int id;
};

How do I call a function in ImagePuzzle from ClickableLabel::mousePressEvent with the ClickableLabel::id passed as argument?

[Edited] Following the suggestions I add a signal, but it is not working. (can compiled but do not call the function in main class) clickablelabel.h

class ClickableLabel : public QLabel {
    Q_OBJECT

public:
    explicit ClickableLabel(QWidget* parent = Q_NULLPTR, Qt::WindowFlags f = Qt::WindowFlags());
    ~ClickableLabel();
    void setId (int id);

signals:
//    static void clicked();
    void test (int id);

protected:
    void mousePressEvent(QMouseEvent* event);

private:
    int id;
};

clickablelabel.cpp

void ClickableLabel::mousePressEvent(QMouseEvent* event) {
//    emit clicked();
    emit test(id);
}

void ClickableLabel::setId (int id) {
    this->id = id;
}

imagepuzzle.h

class ImagePuzzle : public QMainWindow
{
    Q_OBJECT

public:
    ImagePuzzle(QWidget *parent = nullptr);
    ~ImagePuzzle();

public slots:
  void test(int id);

private:

    Ui::ImagePuzzle *ui;
    QVector<QVector<ClickableLabel*> > imageLabelArray;
};

imagepuzzle.cpp

void ImagePuzzle::test (int id) {
    // do something
}