You do not say which desktop you are using. Mageia has lots of different desktops available so it is hard to answer questions unless you tell us.
I am guessing you are using KDE, and you want to know how to place plasmoids on the desktop.
You will find the KDE handbook for the Plasma desktop here
http://docs.kde.org/stable/en/kde-workspace/plasma-desktop/index.htmlYou can find the KDE handbooks in other languages here
http://docs.kde.org/stable/en/kde-workspace/The Plasma desktop is not particularly intuitive . Many people end up deleting their task bar when learning how to use it. But do not panic. It is always possible to recover if you screw it up.
If you want to install more Plasmoids take a look in the Software Install section of Mageia Control Centre. Do a search on plasma and you will find lots of them.
Once you have installed a plasmoid refer to the KDE handbook to learn how to place it on your desktop.