Instructions for mounting an NTFS HD are
here.
Typically you would do something like -
fdisk -l (find out the device name for your NTFS partition, usually /dev/sda1, and the USB drive, /dev/sda2 - fdisk tells you how big each disk is, so easy to spot which is which)
mkdir /mnt/windows
mount -t ntfs /dev/sda1 /mnt/windows
mkdir /mnt/usb
mount -o rw /dev/sd2 /mnt/usb
cd /mnt/windows
<find files>
cp <files> /mnt/usb/