Trouble changing domain name

Once I change the repo name to another domain of my choice, and not my username, a 404 error page shows up. Not sure why this is happening.

[SrIzan10]

If you want to use a custom domain with Github Pages, try creating a file called CNAME, all caps and then you put the domain that you want to use with it. Then you go to the DNS service of your domain and put for name the subdomain name, if you want to use for example example.com you need to put an @, and then for the URL you need to put furuya-san.github.io and you are done!
(sorry for my bad english btw)