I created a new table (named extrapage) in the wordpress database (named wpsite_db). I have added to this table some pages not published directly with wordpress and I want these pages to be considered when searching the site. But I don't know how to proceed. I did some research and learned that I would have to extend WP_query to my new table. But I'm a novice and I don't know how to proceed in real life.

Can someone help me, please? Thank you in advance.