try this:
self. window = [[UIWindow alloc]initWithFrame:[[UIScreen mainScreen]bounds]];
UIStoryboard *mStoryboard = [UIStoryboard storyboardWithName:@"your storyboard name" bundle:nil];
ViewController *VC1 = [mStoryboard instantiateViewControllerWithIdentifier:@"VC"];
UINavigationController *navVC = [[UINavigationController alloc] initWithRootViewController:VC1];
[self. window setRootViewController:navVC];
[self. window makeKeyAndVisible];
return YES;
now inside VC1 push the next view controller to your stack with
// EDIT:
UIStoryboard *mStoryboard = [UIStoryboard storyboardWithName:@"your storyboard name" bundle:nil];
ViewController *vC2 = [mStoryboard instantiateViewControllerWithIdentifier:@"VC2"];
[self.navigationController pushViewController:vC2 animated:YES];