Setting a Default Template
If you have more than one template saved in your account, you can set one of those templates as the default template. The content library uses your default template to format page setup, repeaters, and text styles.
You can set your default template in the Templates section. To do this, hover over a template and click on the white bookmark that appears on the template thumbnail:
Your default template will then have green bookmark image on the thumbnail
See also What are Templates?