Config.php does not exist, please copy config.php.default to config.php

I just got done installing Librenms, when try to validate the install I get this error ( config.php does not exist, please copy config.php.default to config.php) I followed the instructions on the website and I am not sure where did I go wrong with it. Is there something else that I might have left out or not doing?

I guess your install dir should be /opt/librenms

do this:
cd /opt/librenms -> ls -> Do you see config.php ? - if not -> cp config.php.default config.php -> ./validate.php