Navigate back to the Event detail page. If you are the organizer or have administrative privileges, you will be able to click on the button View Attendees to see the list of attendees.
From the attendee list view, use the gear menu to download the attendee data as a CSV file. Also use the gear menu to send event attendees a message.
From the attendee list, you may also add attendees, remove attendees and track attendance and no shows (see article “How do I track event attendees and no shows?”).
A brief overview video is available in this question.