Besides the content of Tiki pages themselves, there are also lots of little words used in the Tiki interface that you might want to translate.
You may first want to mail the webmasters to ask them to make sure they've imported the latest data for your language.
Having done so, go to the box named Menu, Admin -> Edit languages. In the second half of the box, select your language's code, "Translate recorded" and set. Then just walk the list translating things.
Sometimes things take a while to show up. If you'd like them to show up faster, your best bet is to come to the IRC channel and ask rlpowell to clear the Tiki cache.