Create a mount point for the other hard drive. You must be root.
mkdir /mnt/whatever name you want
Then mount the drive. You need to know what device it is and the file system type. Example for a hard drive (secondary master = hdc) with a vfat partition mounted under /mnt/windows
mount -t vfat /dev/hdc /mnt/windows
Then you can just open the /mnt/windows folder in the file manager and copy the files you want to your linux drive. After you are through copying the files you can unmount the drive with: umount /mnt/windows