See the full guide here (link)

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Create a new event with a video meeting

When you add a guest to an event, a video meeting link and dial-in number are added automatically.

  1. Go to Google Calendar and create an event.
  2. On the Guests tab, click Add guests and enter the email addresses.
  3. Click Save.
  4. Click Send to send the invites.
Guests receive an email with the event information and a link to the video meeting. Guests can forward the meeting link to other people. If someone tries to join who was not invited to the Calendar event, a meeting participant from your organization must accept their request.
 
Note: To manually add a video meeting, click Add conferencing.

Copy an existing video meeting from one event to another

You can use the same Meet conference details to schedule Calendar events.

  1. In Calendar, open an event that has a conference call in edit mode.
  2. Next to Join Hangouts Meet, click the Down arrow Down arrow.
  3. Next to Meeting ID, click Edit Edit event and paste or type an existing Meet URL.
  4. Click Save.
Add videoconferencing from web