Google probably has a huge amount of data on your website and you can dig into the data and analyse it with Google Search Console. Here is the start of a series on how to use it if you are not sure what it is or what it can do Getting started with Google Search Console
Once you have submitted a site map, Google will read it again every so often to see if there is anything new on your site. It is automatic and you don’t need to do anything.
SEO plugins for WordPress automatically submit sitemaps to Google, so again it is automatic.
If your site is not updated very often, Google might not check your sitemap very often. It could be a week or even two after posting an article that Google finds the new content. Instead of waiting for Google to get around to reading your sitemap, you could speed things up by submitting it. This won’t force Google to immediately index the new content, but it is faster than waiting for Google’s automated process to do it.