to edit the universal email behavior, open the contactThanks.php page, go to the bindings panel, click the plus button and select Form Data, click the folder icon and select the Form page to add bindings from the form page.
now go to the server behaviors panel and double click the Universal Email server behavior.
In the universal Email behavior click the From button to go to the advanced from settings.
Here you can set the From Display name and the From Address.
The From address is mandatory and must be an email address, the from display name is optional. if you want to hard code the from display name, just enter it. to use the first name and last name:
Click the lightning bolt icon and select the first name form field, copy the code that is added to the from display name field. Then click the lightning bolt icon again and select the last name form field. Place the cursor at the beginning of the from display name box and past the first name code in.
For the from email address, click the lightning bolt icon and select the email address form element.