At the moment, I\'ve been adding navigation buttons like follows:
self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@\"Add\"
As of Xcode 6, it looks like the navigation item on the navigation bar is no longer created automatically.
You'll need to drag out a Navigation Item onto the navigation bar first before you can drag out a Bar Button Item (as detailed in Rob's answer) to add to the navigation item.
You can just drag out a Bar Button Item and drop it on the right end of the view controller's navigation bar: