Edna,
In the past Custom HTML was set up on a per-list basis with each list having it's own Custom HTML. In recent versions of ListMail, however, the Custom HTML section has been 'modularized'. This means you can apply one set of Custom HTML to more than one list. What you need to do is as follows:
1. Set up a new set of Custom HTML pages. Click "List Settings" -> "Custom HTML", then "New".
2. Rename and Save the new HTML set
3. Edit each of the 6 Custom HTML pages in the set to your liking, saving each one.
4. Go back to "List Settings" page for the desired list and choose your new Custom HTML set by name in the dropdown under "Custom HTML".
5. Click Save to save the new list settings
Please let me know if you require further assistance!
Regards