How to create an Instance Variable in Objective-C

I have this example, and I would like to make my_Picture an instance variable in order to use removeFromView. Any Ideas? I got all kinds of warnings and errors trying different approaches. Thank you in advance

- (void) viewDidLoad
{
   UIImageView *my_Picture = [[UIImageView alloc] initWithImage: myImageRef];
   [self.view addSubview:my_Picture];
   [my_Picture release];

   [super viewDidLoad];
}

From stackoverflow

• To make it an instance variable you would store the value in your class instead of as a temporary variable. You will also release it when your class is destroyed instead of after adding it as a subview.

  E.g.

  // header file (.h)
  @interface MyController : UIViewController
  {
    UIImageView* myPicture;
  }
  @end
  
  // source file (.m)
  - (void) viewDidLoad
  {
     myPicture = [[UIImageView alloc] initWithImage: myImageRef];
     [self.view addSubview:myPicture];
  
     [super viewDidLoad];
  }
  
  - (void) dealloc
  {
     [myPicture release];
     [super dealloc];
  }
  

  : Thank you so much. Works perfectly.