How to create back button in navigation bar

Add the following in viewWillappear

     UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithTitle:@"Back" style: UIBarButtonItemStyleBordered target:self action:@selector(Back)];
     self.navigationItem.leftBarButtonItem = backButton;

And in

- (IBAction)Back
  {
    [self dismissViewControllerAnimated:YES completion:nil]; // ios 6
  }