Hi daltonik,

When you say "add a new language" do you mean add a new translation to an existing entry?

If so, the easiest way would be to set the preferred language in your account preferences and as you browse entries you will be presented with an "Translated this item" page if the translation for your selected language hasn't been created. If it has been created, you can head right in to the entry and make edits as you see fit.

Cheers.