Apt is already installed!
Try this:
as yourself, connect to the Internet.
Pop open an Xterm or a Konsole and su to root
then do:
apt-get update
(make a cup of tea)
then
apt-get install synaptic
(synaptic is a relatively user-friendly GUI front end to most of the features of apt-get)
There's lots more about apt get here:
http://www.knoppix.net/forum/viewtopic.php?t=2638
and here:
http://www.knoppix.net/forum/viewtopic.php?t=2638
for example.......