[Support request] display posts based on meta field

Hi everyone,

I have looked through the support area and I can not understand the steps I need to do to display posts base on a meta field and value.
I am using generatepress premium and I have wpsp 1.2 alpha 3 installed. WordPress in running latest version and PHP is 7.xx

I would like to display posts based on the value of the yoast primary category. _yoast_wpseo_primary_category. On my website, I display posts for about for about 18 different primary categories in the sections called “matters of interest” “at the un” and “special features.” Because the editors assign multiple categories to the post, the Yoast primary category helps better identify the content and eliminate duplicates in across the categories. http://www.passblue.com

In support area searching “meta query,” I can see the filters people are using. if I put a sample filter in my functions.php, it crashes the site. Where can I learn how to structure a filter? Where does that filter go? Will that filter add fields to the admin page of wpsp to select a yoast primary category for the posts?

I have been using elementor custom filers. I am looking for a way to reduce my dependence on elementor and its bloated code.

Can anyone point me to some documentation of samples of code that does a similar thing?

I appreciate your help,
John Penney