Customize an auto response for a form I created

Hello administrator,

I'm like to customize an auto response for a form I created. Please advise-

You must be referring to the Autoresponder Email of the form.

Please review our user guide: 

How to Edit the Email Template for Notifications and Autoresponders

You can use the email editor to customize the email content of the form Autoresponder.

Let us know if you need further assistance.