Hi @Clemerson_Campos, 
To set up using the Broadcast service, you will need a couple of flows set up.
Calendar Event Trigger Flow
The first flow will be set to Trigger on the Google Calendar event either being started or the event being created. You will then need to fire a Webhook action in this flow, which will then Trigger the Broadcast Flow.
Broadcast Flow
This Flow needs to have a Webhook Broadcast Trigger. When you set this up you’re given a Webhook URL. This is the URL you will need to use for the webhook action in the Calendar Event Flow. Your 2nd action in this flow will then send a message to all bot users.
To pass the event information across to use in the Broadcast flow you could add the title of the event (or any other details you want passing across) as a query string when firing the webhook in the Calendar event flow. If you do this, make sure when you’re setting up the Broadcast trigger and testing the trigger you include the query string at this point too or you’ll not get any information passed.
We do have a couple of tutorials that may be useful for you to read over too:
I hope this helps 