On Your theme Create Below Files
Archive/Listing Template
– archive-{post_type}.php
Detail/Single Page
– single-{post_type}.php
You can Add your code on that files.
How to Create Theme?
https://developer.wordpress.org/themes/
How to Create Plugin?
https://developer.wordpress.org/plugins/
Coding Standard
https://developer.wordpress.org/plugins/the-basics/best-practices/
