class MenuVC: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        let storyBoard : UIStoryboard = UIStoryboard(name: "Main", bundle:nil)
        let vc = storyBoard.instantiateViewController(withIdentifier: "FourthID") as! CHatVC
       self.navigationController?.pushViewController(vc, animated: true)
        
    }
    
    @IBAction func GoToMessagePage(_ sender: Any) { //its a button to go to message page
        let storyBoard : UIStoryboard = UIStoryboard(name: "Main", bundle:nil)
        let vc = storyBoard.instantiateViewController(withIdentifier: "ThirdID") as! MessageVC
        self.navigationController?.pushViewController(vc, animated: true)
        
    }
   
}

class MessageVC: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
       
    }
    
    @IBAction func GoToChatPAge(_ sender: Any) {//its a button to go to chat page
        
        let storyBoard : UIStoryboard = UIStoryboard(name: "Main", bundle:nil)
        let vc = storyBoard.instantiateViewController(withIdentifier: "FourthID") as! CHatVC
        self.navigationController?.pushViewController(vc, animated: true)
        
    }
   
}

class CHatVC: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
    }

}

in appdelegate add the following code
  
        let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "TabBarID") as! UITabBarController
        self.window = UIWindow(frame: UIScreen.main.bounds)
        self.window?.rootViewController = vc
        vc.selectedIndex = 0
        self.window?.makeKeyAndVisible()