Login/Change of URL Issue

Hello,

I have recently joined the company I’m working at right now and got assigned to redesign their website. The first thing I did is changed the email to mine, as well as the username. I wanted to change the title, but accidentally changed the site’s URL. Now, obviously, I cannot login because the system redirects me to a non-existing page. I’ve tried following instructions in this article (which explains exactly what I did) , but I’m not sure what to do after I’ve edited the wp-config.php file. I suppose I need to upload it to the site using FTP client, but what login info would I use if I’ve changed it?

I hope someone can help me as my first job depends on this.
Thanks in advance.