You don't, for two reasons:
1) Only a published form can be used as a permanent substitute for the standard message form.
2) But, if you use a published form to send messages, non-Outlook recipients will be annoyed at best and furious at worst that they can't read your attachments.
Tell us more about what this template does for you and we might be able to offer a more viable solution.
--
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers