Se non te lo carica dall'Amministrazione prova a metterlo su manualmente seguendo quello che dice qui:
There are certain instances where it may be necessary to manually install mosCE. It is a fairly simple process.
First, if you have attempted to install the mambot with the Mambo installer and this has failed, delete all mosCE files in the mambots/editors directory. These are probably tinymce_exp.php and the mosce folder (and all its contents), but may include mosce.xml.
Next, upload the contents of the bot_mosCE1RC1.zip package to mambots/editors.
In your Mambo administration, got to Mambots->Site Mambots.
Click 'New'.
In the Mambots Details, add the following :
Name : mosCE
Folder : editors
Mambot File : mosce
Hit Save.
Got to Site->Global Configuration, select mosCE as your editor.
