Как сохранить учетную запись facebook в ACAccountStore из facebookSDK

для этого у вас должен быть токен доступа и секрет,

if (self.accountStore == nil) {
    self.accountStore = [[ACAccountStore alloc] init];
}

//make credentials to assign to ACAccount 
ACAccountCredential *credential = [[ACAccountCredential alloc] initWithOAuthToken:accesstoken tokenSecret:secret];
ACAccountType *acctType =[self.accountStore accountTypeWithAccountTypeIdentifier:ACAccountTypeIdentifierFacebook];
ACAccount *newAccount = [[ACAccount alloc] initWithAccountType:acctType];

newAccount.credential = credential;

NSDictionary *options = [[NSDictionary alloc] initWithObjectsAndKeys:
                         "xXXXXXX", (NSString *)ACFacebookAppIdKey,
                         [NSArray arrayWithObject:@"basic_info"], (NSString *)ACFacebookPermissionsKey,
                         ACFacebookAudienceEveryone, (NSString *)ACFacebookAudienceKey,
                         nil];


[_accountStore requestAccessToAccountsWithType:acctType options:options completion:^(BOOL granted, NSError *error) {
    if (granted == YES) {
        [self.accountStore saveAccount:newAccount withCompletionHandler:^(BOOL success, NSError *error) {

            if (success) {
                NSLog(@"the account was saved!");
            }
            else {
                if ([error code] == ACErrorPermissionDenied) {
                    NSLog(@"Got a ACErrorPermissionDenied, the account was not saved!");
                }
                NSLog(@"%@",error);
            }
        }];
    }
    else {
        NSLog(@"%@ ",error);
    }
}];