A file or directory can be deleted using FSEntry_Del():
The second argument, entry_type, restricts deletion to specific types. If it is FS_ENTRY_TYPE_DIR, then the entry specified by the first argument must be a directory; if it is a file, an error will be returned. If it is FS_ENTRY_TYPE_FILE, then the entry must be a file. If it is FS_ENTRY_TYPE_ANY, then the entry will be deleted whether it is a file or a directory.