Before you begin ensure you have your sender entity id and subscriber list ready.
Please pay attention to the naming convention. The naming convention helps Salesforce add the dynamic data with respect to your organization. Such as the header, branding etc. It is as follows
For a formal email
(sender entity id)-F_(name of the file)
ex: PRS001-F_ 0715 Weekly Newsletter
For an informal email
(sender entity id)-I_(name of the file)
ex:BIOD001-I_ July email