Today I was reading a blog post by Dom and he warns you not to edit the Site or Wordpress URL, you can view the blog post here:
https://my.wealthyaffiliate.com/domw/blog/don-t-change-your-website-domain-address-in-the-settings
This short video is going to show you two methods that you maybe able to use depending on your hosting and if you have access to FTP.

Method 1 PHPmyAdmin: Editing the blog database via PHPmyadmin - This isn't available within WA hosting but not everyone uses WA hosting so I decided to include, plus this is the correct way to fix the problem.

Method 2 FTP: Editing the wp-config.php file, it's a very simple method, but you will need to know how to content to your domain via FTP.
Not sure how: https://my.wealthyaffiliate.com/training/ftp-filezilla-connecting-to-domain-via-ftp

Here are the two line of code that you will need to paste into the wp-config.php file, change 12345.com with your domain.
define('WP_HOME','http://12345.com');
define('WP_SITEURL','http://12345.com');

Method two is hard coding the site url, next time you visit the blog general setting page, you'll no longer have the option to edit the Wordpress and Site URL.

What About Free .SiteRubix.com Site

At this moment FTP access isn't granted so if you mess up something you'll need to start over.

Maybe Kyle or Carson can setup new siterubix installation so the option to edit these fields is disabled.

Do You Have A Wordpress Backups

Whenever a mess up or break my sites I'm never really worried because I always have a complete backup of the entire site. I have all my site automatically backed up and sent to a free Google Drive account.
Below are a few different tutorials that will teach you how to backup a wordpress site:

BackWPup plugin tutorial, automatically backup and send to a free DropBox account
https://my.wealthyaffiliate.com/training/how-to-backup-entire-wordpress-blog-have-it-auto-sent-to-a-free-dropbox-account

Wordpress for Google Drive plugin tutorial, automatically backup and send to a free Google Drive account https://my.wealthyaffiliate.com/training/how-to-backup-site-send-to-google-drive-account

Manually backing up site content, super easy and fast but does not backup images, plugins or themes. https://my.wealthyaffiliate.com/training/backing-up-your-wordpress-files