In order to apply special settings to your DocumentsCorePack Template, you have to access the Template Settings Dialog.
How to get to this essential dialog is outlined step by step in this article.

Certain properties of DocumentsCorePack templates consist of fixed text
and Dynamics 365 fields. There are also some additional function calls available and data
from Dynamics 365 can also be manipulated.

Template settings are additional capabilities that can be defined in your DocumentsCorePack templates.
The purpose of most of the settings is to improve the automation of the document generation process.

The Document subject property allows you to define a subject, or a subject pattern for your template. If you only set a document name, the document name will be set as subject as well. So when you use the [Create Activity]-button form the Client, the subject will be already prefilled in the creation dialog.
Please note: This setting only affects the DocumentsCorePack Client Based process!

You have created or modified a new template and now you would like to give
it a try. You can test your template with DocumentsCorePack Client.

This article outlines the functionalities of the [Insert field]-button.