VoiceSDK Text-To-Speech offline

I am using VoiceSDK Text-To-Speech in my app, which needs internet to get the response, instead i want it to work offline, so i got the Preloading TTS Files docs to load it in offline , but the documentation is so less to understand the implementation , so any help is so much thankfull.

https://developer.oculus.com/documentation/unity/voice-sdk-preloading-tts-files/