modify jlabel according to user logged in java

I need to modify a Jlabel of the main page according to the user that has logged in in the Login Frame.

I leave the code that I am working on, in case you can help me. I remain attentive to your answers

  void generarNombre() {

    String sql = "Select CONCAT(nombre_usuario, ' ', apellido_usuario) As Nombre From usuarios;";
    conectar cc = new conectar();
    //    Connection cn = (Connection) cc.conexion();
    try {
        java.sql.Statement st = cn.createStatement();
        ResultSet rs = st.executeQuery(sql);
        while (rs.next()) {
            //Aca le digo que muestre el valor en un JtextFiel

            lb_usuario_recepcionista.setText(rs.getString("Nombre"));

        }

    } catch (SQLException e) {
        // NOTA: So hubo error muestra el error
        JOptionPane.showMessageDialog(null, e);
    }
}