How to change what it says when my blog comes up

Try looking at the site tagline in Setting -> General

If you look at my blog now, I’ve put Springfield Missouri Senior Portrait Photographer. That shows up above my title, but the browser bar still says the old statement.
https://www.jasonmportraits.com/Blog/

Is that info in my main html file I’ve uploaded to my website?

your site is using a seo plugin; check the settings and entries for that text.