Forms notify a specified person by email when an entry is received. To notify the registrant, the person who completed the form, click the Forms button, and hover under the label of the form you wish to change to make "Edit" appear, and click on Edit. On the new screen, hover over Form Settings and click Notifications. 

Select Registrant Notification.

A notification message is required. Enter the message you wish to send to the registrant.

Click Update Notification when finished.