On my page it look something like this...
$RecipientEmail = "".((isset($_POST["email"]))?$_POST["email"]:"") ."";include("WA_Universal_Email/WAUE_Application_Form_2.php");
In the wizard, under the To tab, click add
then click the lightning bolt next to the entered value
then in the pop up, expand the option for your form
Then select the form element where your user enters their email address.