Dunno if you're using the CD or a HD install.

You want a line in /etc/fstab (if it's a HD install, it's probably already there: just remove the # in front of it):

/dev/sda1 /mnt/sda1 vfat noauto,users,exec,sync,umask=000 0 0


(Note that this assumes that /mnt/sda1 already exists -- if not, create it, also that your usb drive is formatted with some kind of fat, if not, change the filesystem type)

then (as root) do

mount -a