Accidentally Changed URL in General Settings

I’ve done the no.1 ‘DO NOT DO’ and changed the URL for my wordpress site under General Settings and now am no longer able to get to my site. I’m super new at all of this and so far as I’ve read, I need to either:

  1. Access the FTP and edit the URL there - I have no idea where/how to find the FTP for Local, so that hasn’t worked.

  2. Add some code to the wp-config.php doc - have tried adding define(‘WP_HOME’, ‘http://sitename.com’); define(‘WP_SITEURL’, ‘http://sitename.com’); to the doc on my hard-drive but this has not worked

  3. Access the site by using the url with /cpanel at the end. Which also has not worked.

Feeling very silly and frustrated at now not being able to access my site for two days. If anyone can help I’d really appreciate it. Thanks in advance!