Anh,
Sorry, it took so long for a response. We had to do some research on this as it's not something we've done before or had requests for how to do.
From what I can tell, here's what you need to do:
* Go to your Facebook Application Settings
* Click "Localize"
* Select the language you want to localize into
* Click the "Advanced" settings link in the top right of that section
* In the new window, you'll see a dropdown for "Strings" and another for "Language".
** The Strings dropdown will show all the strings you've configured for your base/primary language
** The Language dropdown can be used to select any other language you want to support. Once selected, you'll see all of the language strings you've configured for the 'primary' language and you can set the string for the 'other' language.
From your image, your primary language is Vietnamese. If that's the case, the Open Graph language strings you create in the Open Graph area should be in Vietnamese. You should set all settings in your App in the primary language you want to use. You can use the Localize area to translate any language strings from your primary language to other languages.
The default for all of your strings should not be English, it should be whatever language you have configured for your application.
I hope that helps explain and get you going. Should you have any questions, just let me know.
Thanks,
Alex