Q: changing path in site URL?

[sloanlance]

I forked jekyll-now a few years ago when I thought I'd start writing a blog. Things happened, and also I probably didn't have as much to write as I thought I would, so the site as gone untouched. Now I have things to write about and I will revive the site. The first thing I want to do is change the path to the site in the URL. That is…

• Current: https://sloanlance.github.io/
• Wanted: https://sloanlance.github.io/fubar
  I thought I could do that by changing _config.yml in my repo. I changed the baseurl as I thought the comment was suggesting…

# If you're hosting your site at a Project repository on GitHub pages
# (http://yourusername.github.io/repository-name)
# and NOT your User repository (http://yourusername.github.io)
# then add in the baseurl here, like this: "/repository-name"
baseurl: "/fubar"

However, that didn't move my site. It only broke the styling at the current URL and requesting the /fubar URL only gives an HTTP 404 error. What's the correct way to move the site?