1. Go to the event page.
  2. Click the Menu [...] button.
  3. Click Send notification.
  4. Type your message.
  5. There will be five checkboxes for groups that you can send the message to.
    1. All attendees [selected]
    2. All organizers [selected]
    3. All viewers [selected]
    4. Custom
    5. Send me a copy [selected]
  6. Click the checkbox to select or deselect a group.
  7. Click Send.