Lost website error 404

So, I was trying to change the URL by changing the general settings of my site and now all i get is an Error 404 message, which means I cannot log into the backend anymore. I see this linked response all over this forum, but I don’t understand how I can put the code in if I can’t get into the backend anymore? I.E. I can’t get into the general settings or find the wp-config.php…Please help!

And this phpadmin thing… my sites are hosted via bluehost… any tips there?