Tagging @mtub, who manages translations.
There are a few ways to work with translations -- you can use the Translator plugin, or work with the XML files directly. Make sure that you're putting translation strings in the file that corresponds to where they appear in the English translation. Depending on what operating system you're using, you can search the English files for strings by name. For example, in a Linux environment I could run...
fgrep -l -i common.homepagenavigationlabel `find . -name \*.xml | grep en_US`
Public Knowledge Project Team