Hi. I don't know anything about Knoppix, but if the raid device has already been setup, and is separate from the actually system (you don't need it to boot up) then there should only be two main aspects to this. One is getting mdadm and your mdadm.conf file set up, and the other is setting up fstab to automatically mount the raid device.
It would be ideally to find documentation written for your own distro, but a quick google search pulled this link up:
Look through the section "Create the mdadm.conf Configuration File" and the sections following to get a rough idea. Also, if you can take a look at the mdadm man page and learn how to do this manually, it will give you a better understanding of what is going on.
[edit: Oh, err... is that a hardware raid configuration? I assumed software raid when I skimmed through. My info probably isn't relevant. Apologies for wasting your zero-reply status.]