If I understand the content of altervista correctly, it's a site where they offer free hosting. And you have a forum hosted on altervista that you want to move onto the .com domain you have registered at godaddy. And now you want to self-host your forum on the .com you have registered. Is that correct? If so, what type of forum do you have (phpBB, WordPress/BuddyPress, or another framework)? Answering that will help us help you.