Modified the iOS + Facebook sample from: https://parse.com/tutorials/integrating-facebook-in-ios

AppDelegate.m

//
//  Copyright (c) 2013 Parse. All rights reserved.

#import "AppDelegate.h"

#import <Parse/Parse.h>
#import "LoginViewController.h"
#import "UserDetailsViewController.h"

@implementation AppDelegate


#pragma mark - UIApplicationDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    
    // ****************************************************************************
    // Fill in with your Parse credentials:
    // ****************************************************************************
    [Parse setApplicationId:@"id" clientKey:@"key"];

    // ****************************************************************************
    // Your Facebook application id is configured in Info.plist.
    // ****************************************************************************
    [PFFacebookUtils initializeFacebook];

    // Override point for customization after application launch.
    self.window.rootViewController = [[UINavigationController alloc] initWithRootViewController:[[UserDetailsViewController alloc] init]];
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];
    
    LoginViewController *lvc = [[LoginViewController alloc] init];
    [self.window.rootViewController presentViewController:lvc animated:YES completion:nil];
    
    return YES;
}

// ****************************************************************************
// App switching methods to support Facebook Single Sign-On.
// ****************************************************************************
- (BOOL)application:(UIApplication *)application openURL:(NSURL *)url sourceApplication:(NSString *)sourceApplication annotation:(id)annotation {
    return [PFFacebookUtils handleOpenURL:url];
} 

- (void)applicationDidBecomeActive:(UIApplication *)application {
    /*
     Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
     */
    
    [FBSession.activeSession handleDidBecomeActive];
}

- (void)applicationWillTerminate:(UIApplication *)application {
    /*
     Called when the application is about to terminate.
     Save data if appropriate.
     See also applicationDidEnterBackground:.
     */
    [FBSession.activeSession close];
}

@end