Duplicate question: UIButton : Multiline text .
But in your case:
    UIButton * viewedYou = [UIButton buttonWithType: UIButtonTypeCustom];
    viewedYou.frame = CGRectMake(0.0,0.0,61,30);
UILabel* viewedYouLabel = [[UILabel alloc] initWithFrame: viewedYou.bounds];
    viewedYouLabel.backgroundColor = [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.0];
    viewedYouLabel.textAlignment = UITextAlignmentCenter;
    viewedYouLabel.frame = CGRectMake(0.0,0.0,61,30);
    viewedYouLabel.numberOfLines =2;
    viewedYouLabel.text = @"Viewed\nYou";
    [viewedYou addSubview: viewedYouLabel];
    [self.view addSubview:viewedYou];