how to remove "Built with concrete5 CMS."
To remove the "Built with concrete5 CMS." text from the bottom of the Elemental theme, you need to remove or comment out line 62 in footer.php
concrete\themes\elemental\elements\footer.php - line 62
This solution is only temporary, when you update concrete5, the changes will be overwritten. To make these changes permanent, you will need to make a copy of the theme. The following How-To explains how to copy the Elemental theme.
Is this live editor a feature of your web host?
This file can also be accessed and modified using FTP.