Create a swift file (SecondViewController.swift) for the second view controller
and in the appropriate function type this:
let secondViewController = self.storyboard.instantiateViewControllerWithIdentifier("SecondViewController") as SecondViewController
self.navigationController.pushViewController(secondViewController, animated: true)
Swift 2+
let mapViewControllerObj = self.storyboard?.instantiateViewControllerWithIdentifier("MapViewControllerIdentifier") as? MapViewController
self.navigationController?.pushViewController(mapViewControllerObj!, animated: true)
Swift 4
let vc = UIStoryboard.init(name: "Main", bundle: Bundle.main).instantiateViewController(withIdentifier: "IKDetailVC") as? IKDetailVC
self.navigationController?.pushViewController(vc!, animated: true)