How to edit /usr/bin/mkdesktophdicons in a TOHD install

I'm using knoppix 3.8.1 and was told that i could edit this file when ver. 3.8.1 with unionfs came. Now it's here and I'm trying to find out how to do this. I have a edited version of mkdesktophdicons that puts the icons in a folder instead of on the desktop. My question now is how to move this file to /usr/bin so it replaces the original (or edit the original with the changes).

I'm booting from a usb2 hdd with knoppix 3.8.1 tohd installed on /dev/sda1 and home on /dev/sda2

As you probably can tell by now I'm quite new at linux/knopppix but trying to learn as much as possible.

/W