How do I add a site description that will be visible on a Google search?

Jay:

The Google results tell you what the problem is with your site – robots.txt. This file defines what search engines (robots) are allowed to do on your site. Whether a search engine follows your rules is up to the search engine.

If you go to: https://www.jaymarkjohnson.com/robots.txt you’ll see that your robots.txt file says that robots are not allowed to search the site starting at the root ( as indicated by the / ). So Google won’t put anything in the description it displays in the Google results.

You need to edit the robots.txt file. If you don’t know how to do this, install this plugin: https://www.ads-software.com/extend/plugins/wordpress-seo/ It provides a way to edit the robots.txt file.

Here’s what www.ads-software.com suggests for the robots.txt file:
https://codex.www.ads-software.com/Search_Engine_Optimization_for_WordPress#Robots.txt_Optimization

Here’s what Yoast recommends for the robots.txt file:
https://yoast.com/example-robots-txt-wordpress/