No no my friend, I should have made myself clearer.
Installing, is almost always a sys admin function - hence you have to be "root" first.
The way mandrake accomplishes that, is that you click the "configure my computer" icon on the task bar - it then asks you for your root password, you put that in and hit enter, bingo you have root permissions to do that sort of stuff.
From there, the icon for software manager, click it and you should be presented with 4 (I think) options - the ones you want too look at would be RPMdrake + and RPMdrake -, those are the ones that you'd normally have to use for installing/uninstalling stuff.
Additionally, you would be better placed to make sure that the sources are OK i.e. that the application knows where to get packages from (thats new packages as well as updates and stuff like that). Thats where the "easy urpmi" link I posted comes in. You literally follow the instructions for your version and architecture (x86, amd64, whatever your system is) use the dropdowns to get the mirror addresses that are closest geographically to you (normally, but if one of them turns out to be crap for some reason then try a different one for which ever source is a nuisance). follow it down and when you get the out put in stage 3 (I think, it might be 4), you need to open a konsole/terminal window - and then you need to become root again (thats where you type in "su" without the quotation marks, hit enter, input root password and enter, the prompt should change from one ending in $ to one ending in #), the output stuff from the easy urpmi is then copied and pasted into the terminal/konsole window (you may have to hit enter afterwards - I had to sometimes and not others).
Let it do it's thing, then when it's finished doing the updates etc thats when you move back to the Software manager window and start applying updates and installing packages etc.
It all sounds rather drawn out - but it's not really. When you've got the sources up to date it enables you to do the regular house keeping of the system to keep it up to date and secure.
From easy urpmi, you'll probably need sources for main, contrib, jpackage, updates, plf-free and plf-non free. Oh and you can also then dump (delete) the source listing for the CD(s)/DVD - as they'd already be out of date.
For installing packages, rpms (the packages) are made/build for individual distros - and untill you get up and running with this, you will be best placed by only installing "mandrivised" rpms - if you attempted fedora ones, or SuSE ones, it's likely that you'd end up in "dependency hell" (dependency problems that spiral, you need package a, which try to get, but can't because package a is a dependency of package z, you try to get package z, but can't as it's dependent on package b, etc etc).
The same tends to apply to source packages.
The command string that your friend looks like it mounted the cdrom and then copied either the package list or actual packages over to the system.
I'm trying to explain the easiest/safest way of doing this as you have missed something fundamental at the installing the distro stage.
Maybe that helps some ?????
p.s. it may be that you can find an answer at the LQ distros>mandriva forum or of course there is also some very distro specific help located here
but they don't tend to answer as quick as here at LQ (theres less of them).