Where to enable
On Settings → Integrations each integration has a connect button. The connection uses secure OAuth to your account; you can remove it any time.
Free plan 30-day trial
If you're on the Free plan and haven't used it before, you'll see a one-time offer to try Google Calendar + Meet for 30 days. After it ends, an upgrade is required for continued access.
What you can do
With Google Calendar your appointments are written to your calendar, and with two-way sync your external events appear as busy. With Google Meet or Zoom a meeting link is generated automatically for online appointments.