As you can see in the picture below, my UIViewController IS NOT a UINavigationController, it's a common UIViewController. What I did is I put a UINavigationBar using interface builder and above it I put a UIImage. The problem is that I want to change the font of this UINavigationBar. Anyone would have a clue on how to do it?

Usually, with a common UINavigationController I use the following code:
// this will appear as the title in the navigation bar
self.label = [[UILabel alloc] initWithFrame:CGRectZero];
self.label.backgroundColor = [UIColor clearColor];
self.label.font = [UIFont fontWithName:@"Copperplate" size:22];
self.label.shadowColor = [UIColor colorWithWhite:0.0 alpha:0.5];
self.label.textAlignment = UITextAlignmentCenter;
self.label.textColor = [UIColor whiteColor]; // change this color
self.label.text = [self.navigationItem title];
self.navigationItem.titleView = label;
[label sizeToFit];
