Once your have published your event to the website, the public will be able to book onto your event online.
You can also add attendees manually using the Check In App and from within the 'Attendees' tab of your event page, by selecting the 'Add attendees' button:
Now fill in the details of the attendee:
You can also add additional group/family members using the '+ Add friend/family member to this group'button.
Once saved, the attendee(s) will appear in your attendees list and will also be added to your contact module with an open days tag: