To use a normal "LIVE" knoppix cd/dvd/usb the trick is just to boot to the knoppix system. It should allow you to use the common tools to open up partitions. The partitions ought to show on desktop but may depend on version.
If you want you can use the file managers in it. You may have to open files or file manager as a super user.
Many of the knoppix disks come with no password so you may first have to create one. From command line use command sudo passwd