look in file "/etc/fstab".
you will see there line like:
# /windows was on /dev/sda7 during installation
UUID=703CD5D83CD59A04 /windows ntfs defaults,umask=077,gid=46 0
change the umask, and then do "umount" and after that "mount".
NTFS can't save UNIX type permissions, therefore you can apply only one
umask to whole the FS.