Instructions for Google TTS Json Key

I installed the plugin and it’s working well. I was able to figure out Amazon Polly but for Google TTS, I am struggling to figure out what exactly to do to set this up correctly. I have copied the entire JSON code and then tried to just copy the private key, either way I just can’t get it to work. Or maybe, I don’t have the right setting in Google Console. What would be helpful is more detailed instructions on how to set up Google TTS correctly. Even a quick video screen share walking thru the steps would be helpful to get this to work properly. Thank you so much in advance.