I have found this post about how to add localization to an app. The answer is very extensive and very helpful.
There is just one thing:
When selecting the 'Localizable.strings' file I open the File Inspector and I click on the button 'Make localized..' within the Localization pane. In the pop-up I can select a language but there is actually only one language to select form; English. There are no other options. But OK, having the option English selected I click on the button 'Localize'.
Now, in the file inspector, within the Localization pane I see the option English selected.
My problem: I do not have a '+' button to add an additional language.
Doe anybody know what is causing this? How can I add an additional language? I am using Xcode 4.4.