Hi Kjetil. Welcome to translatewiki.net! You can now start translating. You should also check the portal for your language, the link is in the sidebar. Other useful pages are linked in the translatewiki.net menu that comes with this message.
Your translations are transferred to the standard product every few days or every few weeks depending on the product. Please notice that it may take longer before you see your translation in the actual product. It can be just a few days before they appear on Wikipedia, but a few months can pass between each new release of FreeCol.
We wish you a productive and pleasant stay. Please leave any questions on Support. Cheers!