legacy and file not found:

I have installed now mosets tree 3.06 buid 122 on joomla 1.5.2 ita stable
on http://www.forniture-alberghiere.net
at the first import of file com_mtree-206_build122.zip the system tell me to go in activate the legacy mode.
I do that and I try again to upload com_mtree-206_build122.zip but now the system give me the page: 404 file not found
I have done something wrong?
what I must do to install mosets tree last version into italian joomla last version?

I need to put mosets tree instead of adsmanager and put in only as directory , in similar way like this: http://demo.templateplazza.com/classified_plazza/