In the Software>ConfiguremediaSources GUI click on 'Add' and 'Full Set of Sources' and it will add the define all the sources for you as $MIRRORLIST meaning it will dynamically download from whichever mirror is near you and working.
The 'tainted' and 'nonfree'' repository is disabled by default. Enable tainted to access packages that were previously in PLF in Mandriva. There is no need to go to PLF any more.
If you want to add a specific mirror a list of mirrors is here
http://mirrors.mageia.org/Use urpmi.addmedia just like in Mandriva to add them