From Facebook Developer Wiki

Preparing your Platform Application or Facebook Connect Site for Translation

In order to opt into the Facebook Translations framework, there are a few settings you need to edit for your application. You need to set the native language for your application, then you need to decide into which languages you want your application translated.

Selecting Your Native Language

1. Go to the My Applications page in the Facebook Developer application, where you initially configured your application.
2. Select the application you want translated, then click Edit Settings.
3. On the Basic tab, select the Language in which your application is currently written, then save your selection. This selection determines the native language from which translations will occur.
   

Managing Languages and Translations

1. Visit the Translations admin panel for your application. If the default selection is not the application you wish to translate, select the right one from the dropdown in the upper right corner.
   
2. For each language, do the following.
   • Enable it for translation: To enable translation of your application into a particular locale, select the row for the appropriate Language, then check the On check box for that locale. After checking it, users can see any strings that you mark as translatable, and can provide translations for them.
     Note: If this check box is NOT checked, the only people who can translate your application into this language are the application's developers (listed in the Facebook Developer application) and those designated as the language managers for this language (see the Language Managers column).
   • Review translated strings: Click the link for the language in the Language column. You are taken to the Browse Strings tab for text in this language.
   • Check the progress of the translation effort: The progress bar in the Translation/Approval Progress column gives you a high level idea of what percentage of your text is translated and/or been approved (the approval process is described in Administration).
   • Specify language managers: In the Language Managers column, specify which Facebook users can administer translations in the given language. These individuals may view, add, and remove translations regardless whether the application is open to all translators.
   • Publish in that language: When you decide that the existing translations are sufficient, click the blue Publish link. It turns green and changes to Published, which indicates that all users that view your text while viewing Facebook in this locale will see the translations. Additionally, if your application is (or becomes) available in the Facebook Application Directory, then it will show up there in the newly published locale.

Note: Once you initiate the translation process, you'll return to the Translations dashboard when you need to do more administration. For now, these steps are the ones necessary to get started.

Congratulations, your application is ready to start the translation process! Now, register the text you want translated.