Xcode, in all its mind-bogglingly incomprehensible wisdom, makes the simple act of renaming a folder a chore. If you’ve ever used any IDE ever released on any other platform in the history of computing, you would think it would be as simple as right-clicking (er, command-clicking) on the folder and selecting ‘Rename’. Sadly, no. There’s no rename option. But wait – there’s a ‘Group Name’ option in the File Inspector. Just change that and… nope. That just changes the name as it appears in Xcode, not the name of the actual folder on disk. What you actually appear to have to do is rename the folder in Finder, then click on the little folder icon in the File Inspector and point the group to the new folder.
Oh, and don’t even think about renaming your project. That would just be stupid.