Blue folders in Xcode appear as actual folders in your app's bundle. This means you need to include the folder name in the file's path in your code:
NSString *bundlePath = [[NSBundle mainBundle] bundlePath];
NSString *folderPath = [bundlePath stringByAppendingPathComponent:@"folderName"];
NSString *path = [folderPath stringByAppendingPathComponent:@"config.xml"];
Replace folderName
with the actual name of your folder.
Or you can do:
NSURL *xmlURL = [[NSBundle mainBundle] URLForResource:@"config" withExtension:@"xml" subdirectory:@"folderName"];