The only people who have access to edit an event are leaders who created the event or admins. This must be done via the website.
- Click on the event on the calendar and click Edit
- Click on the + sign next to Sent to:
Click in the search bar or click on view roster
Make sure you are selecting it as a group and not individual members, unless that is necessary.
Send out notifications to the people you invited or withdrew so they are alerted to the change