Issues with _config.yml in Hitchens Jekyll theme

Hi! This isn’t my first time using a Jekyll theme, but it’s my first time using one in a while.
I’m trying to set up a github page using the Hitchens Jekyll theme, but when I change the baseurl and url in the _config.yml file, the theme seems to stop working.
I’m not super sure what I’m doing wrong. I’m simply updating baseurl to /blog and the url to what I believe the correct url should be- the url for the page.
Any insight or suggestions?
Best- Abby

A good article covering site.url and site.baseurl: