The script needs 'google credentials' but your instructions don't mention either changing this or where to get them from.

[ZoeESummers]

Are we supposed to have access to yours?

You have this in the script:

STTS.GOOGLE_CREDENTIALS = "C:\Users\Ciaran\Downloads\googletts.json"

[ciribob]

Nope you need to setup your own, that's just an example

[ZoeESummers]

Do you have instructions on what exactly needs to be done and how?

[ciribob]

You need to get your credentials file

https://cloud.google.com/text-to-speech/docs/create-audio-text-command-line

I'd try a Google guide but once you've got you're credentials JSON it's straightforward from there

You need a credit card and billing address etc.