How to configure internationalization?

Hi, I just setup my own Wiki using xwiki-1.0-beta-2.war (Win2K, Tomcat 5.0.27). The web gui is presented in english language and I wonder how to put this into german. I changed the "Default Language" to "de" ("Multi Lingual"="no") but nothing changed so this doesn't seem to be the right way. Any hints? Guido