1) Get the Local Google Concierge Server running.
2) Make sure it sees your Google Home And/Or Google Cast device(s) ... and the Vera(s) that will be issuing the TTS requests.
3) Verify Local Concierge can do Text To Speech (See Text to Speech Tab on Vera Concierge)
4) Install Vera Alerts Plugin on Vera
5) Create a Profile for Vera Concierge
Specify Google Home and or Google Cast for destination of alerts (can be "All")
6) In Settings ... associate the new profile with one or more Vera Users.
Create a notification on a device ... Specify the user to receive the notification (via the associate above, it will send to this new profile)