The first post in this thread has examples of what Certbot commands to use.
For example, if you used "certbot --apache -d example.com -d www.example.com" before, you might use "certbot --authenticator webroot --installer apache --webroot-path /var/www/example.com/public_html -d example.com -d www.example.com", if that's how your web server is configured.
We can't say anything precise without knowing more about how the web server is configured and what commands were used before.
There isn't a guide for editing the files, no. I don't recommend it, especially in a thread with thousands of views.