Ok it's clear now.
Create a SubTemplate from XML Publisher responsibility . It is similar to creating any other template, only the SubTemplate poplist should have value 'Yes'.
Then upload the subTemplate.rtf .
Then in the primary template call it :
- AR - Short Name of the SubTemplate Application
- XX_SUB - Code of the SubTemplate
- en - Language of SubTemplate
- 00 - territory of the SubTemplate. If nothing is given (while creating subTemplate) , you can pass 00