OK, I read through this thread and decided to use the "About Us Page" mod here.

This enabled me to create an internal page defined as PAYMENTS which I edited in the define pages editor from Admin.

I have it added to my drop down menu now and the link is working well....

However, instead of reading, "Payments" it reads, "HEADER_TITLE_PAYMENTS"

I have a file in includes/extra_datafiles/ called payments_filenames.php with this:

define('FILENAME_PAYMENTS', 'payments');

Does anyone know what I've done wrong?