Changed Site URL through Settings>General and now site is offline

I used HostGator this afternoon to quick install WordPress. When it asked for URL, I added a string because I thought it was for login only, and wanted to make it non-obvious.

It instead, though, made the whole site direct through that string, and the main site (plus1keyboard.com) would not work.

So I changed it, and now all I get is a 404 message and am unable to log back in to change it. I found a guide that side to copy and paste:

define(‘WP_HOME’,’https://plus1keyboard.com’);
define(‘WP_SITEURL’,’https://plus1keyboard.com’);

into wp-config.php, but I cannot find where that file is to actually install it. Plus the support response was from five years ago so it may not work.

Does anyone know away to fix this without changing the root file, or if not, how can I go about changing the file, as searching for it through find did not uncover it.

Thanks.