procedure TForm1.TabbedNotebook1Click(Sender: TObject);
var
  myE: TEdit;
begin
  with TabbedNotebook1 do
  begin
    if PageIndex = 1 then
    begin
      myE := TEdit.Create(Self);
      myE.Left := 12;
      myE.Top := 12;
      myE.Parent := Pages.Objects[PageIndex] as TWinControl;
      myE.Show;
    end;
  end;
end;