I have udpated the constant wp_lang to zh_CN, and my wordpress has been changed to chinese, but rtMedia is still in english. I have seen there is file called rtMedia-zh_CN in languages folder, how to make it work?
By default we don’t have translations available for all languages. You can check the status of translated words for your language here : https://rtcamp.com/translate/projects/rtmedia/
If you want, you can add missing translation. It will help the community and it will be updated in next release. Please check this doc: http://docs.rtcamp.com/rtmedia/translations.html for how to contribute to rtMedia and add-ons translations.
I am able to translate that, but once I am done that, how to switch the language?
My question is not about the translation, it is about how to switch the language with the .po and .mo file