How do I change the file and folder permission on the ReadyNAS that is attached to domain controller?

You can use Windows ACLs to do this – right-click on a file, select Properties, then the Security tab. From there, you can set the permissions as desired. Most Windows operating systems will have this feature. Some, such as Windows XP Home, do not. To get the Security option to show under properties, you may need to uncheck the “simple file sharing” option in the Folder Options/View menu.