_fireIcon = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"flame_icon.png"]];

_fireIcon.image = [UIImage imageNamed:@"flame_icon.png"]; // or  [_fireIcon setImage:[UIImage imageNamed:@"flame_icon.png"]];

_fireIcon = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"flame_icon.png"]];

_fireIcon.image = [UIImage imageNamed:@"flame_icon.png"];

[myImage setImage:[UIImage imageNamed:@"5.jpg"]];

NSBundle *bundle = [NSBundle bundleForClass:[self class]];
UIImage *image = [UIImage imageNamed:@"image" inBundle:bundle compatibleWithTraitCollection:nil];
UIImageView *imageView = [[UIImageView alloc] initWithImage:image];