The packages you need to install are gcc (gnu c compiler) and it's associated support libraries.
If the system is set up ok then type (as root)
urpmi gcc
All the necessary dependencies should be taken care of for you.
If you're going to be compiling source code then you'll soon find you also need the -devel rpm's for a lot of the other installed packages. They're usually either on the cd's or available via
http://rpm.pbone.net or other rpm search sites.