Hello,
First of all, thank you for your purchase.
The post subtitle feature is not a WordPress standard feature, but it is a functionality which is provided by your theme. Because of this, the Newsomatic plugin does not have a settings field for it. However, if the subtitle is stored by your theme in a custom field or custom taxonomy, the plugin will be able to add content to it.
Please contact your theme’s support and ask them how they store the data from the post subtitles, in the back end of WordPress. Ask them also how you can automatically add content to the subtitle field from a plugin. Please get back to me with this information.
Regards, Szabi – CodeRevolution.