To follow step 3 of the steps, you would need a true text editor. The editor doesn’t have to do anything fancy as the goal is to work with basic text files. A word processor will not work due to the formatting the processor would do to the file. If you are using Linux, there should be a basic text editor to edit the file. Do not use LibreOffice Writer as this is a word processor. Consult your particular OS for a viable text editor, but assuming for the programming community in Linux, there should be an included basic text editor.
If using a Mac PC, do not use TextEdit for changing the file. This is because TextEdit might save in a .rtf format rather than plain text. I would suggest BBEdit which there is a free version of this application, but the free version works just fine. You may want to set BBEdit to edit .php files unless you are running a web server on your Mac. You can learn more about BBEdit by going to https://www.barebones.com/products/bbedit/.
If you are using Windows 11, then you can use NotePad. This is simple enough if you are just editing on text file at a time. Since you are working on just the wp-config.php file, this will work just fine. If you are using Windows 10, you should either upgrade to Windows 11, or switch to Linux which Linux will have a text editor. Your Windows 10 computer should not be connected to the internet. Do not use Microsoft Word as this is a word processor.