Do you have a gui ftp program installed? If not, you'll need to install one first.
GFTP is quite good.
Then, from your putty console:
Code:
export DISPLAY=:0
gftp &
The first command tells Linux to display GUI windows on the console monitor (and hence your VNC session), and the second command launches gftp. If of course you have a different gui ftp client, adjust the second line accordingly. The '&' causes gftp to launch in the background.
Regards
David