You will have to declare scoreLabel
in the header file and then just so scoreLabel.text = //Your text
anywhere you want.
EDIT:
In your .h file, declare
@property (nonatomic,strong) SKLabelNode *scoreLabel;
In your .m file, add
@synthesize scoreLabel;
When you are initializing the label do
self.scoreLabel = [SKLabelNode labelNodeWithFontNamed:@"TimesNewRoman"];
and not
SKLabelNode *scoreLabel = [SKLabelNode labelNodeWithFontNamed:@"TimesNewRoman"];