Sorry I missed the part where you said this was a power store page.
The Problem is that you cannot have an iRite instance on the page and an HTML Editor Instance at the same time.
before you can add an HTML Editor Instance to the page, you need to update the iRite instances that are already there.
For each iRite Instance, select it in design view. In the property Inspector, click the edit button.
From the editor preset list, select Default File manager Enabled.
then click OK, for the first one, the site preferences will open, select the enable file management option, then click the folder icon next to image upload path and select the the Images/Upload folder.
Once you have updated all of the iRite instances, find the following line:
<?php require_once("../WA_iRite/WARichEditorPHP.php"); ?>
and comment it out:
<?php //require_once("../WA_iRite/WARichEditorPHP.php"); ?>
then test the page.
you can then add in your new form element and apply the HTML Editor to it.