Editing the contents of just one div on a page from wordpress

Welcome to WordPress development! It is a fantastic content management system.

The normal way to display content for a particular page, on that page, is to use the WP function the_content();. This normally entails creating a simple WP loop to check for the existence of content, then perform certain actions (like creating the HTML to display said content).

WordPress Codex is your best reference for this function

… and for writing a basic WP loop

Good luck!