images issues

Hello, when we try to import an image on a page of the wiki 
\"guidermesprojet.com\", after to have logged in, and accessed the page 
\"http://guidermesprojets.com/index.php?title=Special:Upload\";, I have the 
following error message: \"Désolé, l'envoi de fichier est désactivé. \" (that 
is: sorry, message sending is disabled\".
So my question is: how can we activate this feature?
kind regards
Benoit Daloze