I'm not sure if we can help you. Google says:


"After you sign in and set up your screen reader, you can get details on
all features in the Classroom Help Center."


About screen readers, it says:


"You can access Classroom using a screen reader with any modern browser,
such as Chrome, Mozilla® Firefox®, Microsoft® Internet Explorer®, or
Apple® Safari®. See your browser instructions on how to set it up. For
example, you can use ChromeVox with your Chromebook. On Macs, you can
use VoiceOver, the built-in screen reader."


That's for the web, here's what it says about mobile devices, in case
anybody's using those, e.g. iOS, Android.


"Android
The Classroom mobile app works with TalkBack, a pre-installed screen
reader which uses spoken feedback for interaction. For details, see Turn
on TalkBack.
iOS®
The Classroom mobile app works with VoiceOver on iOS®. For details, see
the accessibility settings for your device."


So it sounds like you just log into Google Classroom, and all the
accessibility help for using a screen reader is in there. All of this
stuff about "once you get it set up" doesn't mean special instructions
to set up a screen reader for Google Classroom, I think it just means
getting your screen reader installed or activated on your mobile device
or whatever, then you either go to the Classroom website and login and
all, or set up the app if you're on a phone. Then once you're in, you go
to their help center and they'll tell you about keyboard shortcuts or
whatever they've got.