SimpleTest module Install Error

Hello,

I installed Drupal a few days ago and the install went OK but now I am installing the eCommerce modules and I received this error:

SimpleTest could not be installed. Must add code to the /home/content/i/n/e/inetcult/html/sites/default/settings.php file please see INSTALL.txt. (Currently using SimpleTest code addition Not-found)

Can someone help me out on how to fix this one minor detail?

Thanks in advance :)