Install Facebook iOS SDK

#import <FacebookSDK/FacebookSDK.h>

- (void)applicationDidBecomeActive:(UIApplication *)application
{
  // debug
  [FBSettings setLoggingBehavior:[NSSet setWithObjects: FBLoggingBehaviorFBRequests,
                                                        FBLoggingBehaviorFBURLConnections,
                                                        FBLoggingBehaviorAccessTokens,
                                                        FBLoggingBehaviorInformational, nil]];
  [FBSettings setDefaultAppID:APP_ID];
  [FBAppEvents activateApp];
}

App-Info.plist

<key>CFBundleURLTypes</key>
<array>
        <dict>
                <key>CFBundleURLSchemes</key>
                <array>
                        <string>fb778679942XXXXXX</string>
                </array>
        </dict>
</array>
<key>FacebookAppID</key>
<string>778679942XXXXXX</string>
<key>FacebookDisplayName</key>
<string>MY_APP_NAME</string>