You can customize the confirmation displayed after registration is completed by editing the Event Confirmation Message. You can find this message option on the Attendee Setup tab.
To customize an event confirmation message click the pencil icon.
In the Instructions and Confirmation Messaging window, use the dropdown menu to select a Confirmation Email Template you've already created, or select the plus sign to create a new one.
Enter your own Confirmation Message text.
The Confirmation Message is displayed on the registration confirmation page.
The Confirmation Message is also added to the Confirmation Email registrants receive following their registration if a Confirmation Email Template is not selected.