To customize your HD installed Knoppix (which is Debian), you can just use APT or (better even) Synaptic (=Graphical frontend to APT).
Just open a console in root, and type
apt-setup (if you want to add mirrors)
apt-get update
apt-get install synaptic
DISPLAY=myip:0.0 (insert your IP at "myip")
export DISPLAY
synaptic

Remastering Knoppix basically means that you want to edit the contents of the CD and make a new (customized) version of KNOPPIX ...
You can do this by reading the Remastering-Howto or...
by using my scripts http://www.knoppix.net/forum/viewtopic.php?t=851


Good luck with customizing KNOPPIX, whether it is to create a new CD or just the one on your HD