You must be using Xandros, which comes pre-installed on the eee. I don't have Xandros but I believe there is a "new applications" menu (look for the translation in italian at http://www.google.com/language_tools
) on the left that you can expand and there is a search box to look for software. You have to look for language or i18n: something like language-pack-kde-en or kde-i18n-en.
Install the right language by following the menus: select your package and click install and apply or something like that. Use google language tools to translate.