Hello dear Long
Please follow that link
http://www.seotoaster.com/help-translate-the-toaster.html for translation / localization of SEOTAOSTER.
Click on any Menu item like "Create a page", then select your language : Vietnamese, and then start translating away.
Do not forget to enter the code in Captcha field before saving at the bottom of the page, so you can resume next time you log in if you had not finished to translate the Menu item you were working on.
Then move on to next menu item etc ...
When completed, SEOTOASTER will mention you as an official contributor to the translation of this awesome CMS.