to install the kernel sources type this:
# urpmi kernel-source-YOUR.KERNEL.VERSION
type 'uname -r' to get YOUR.KERNEL.VERSION
note the # at the front, indicating to do this as root. The way to get to root is the 'su' command. Hence, If i wanted to install my kernel sources, I'd do this.
$ uname -r
# urpmi kernel-source-2.4.25-2mdk
It will then provide a status indicator, and so on