Each page within the authors app has its own template to display that page's content.
Where to save template files
Template files will go in the authors folder inside the templates folder.
If your theme was called "Custom" then this would be an example folder structure:
Authors app pages and their templates
Below is the list of the Authors app pages and the name of the template file that you should create.
The main page for the app shows the list of authors.
Template name: main.twig
This page shows a single author.
Template name: author.twig
This page shows the list of authors.
Template name: authors.twig