How to change config file to read only

I am brand new to modx. Forgive my elementary question. I spent hours on the Forum
but cannot the answer.

After successful installation, I received this warning message -

"One or more configuration details didn’t check out OK:

Configuration warning: Config file still writable! "


I am working on my own computer. I look at the config.php file but cannot see any file permissions (0666.
How do I change the permission?
Thank you

If your OS is Windows, just go into the file manager and find the file manager\includes\config.inc.php, right click to it and choose properties. There you can tick the Read only option.

Thank you Ottogal for your quick response.

Problem resolved