Johnny91 Your setup is a bit unclear ... You don't even explain where your main root is for both. One would assume that is public_html, but then you are asking how to assign this in your first question.
Johnny91 The main index.php is inside public_html
How do I point it correctly?
If you want the main index.php to read files from directly inside public_html, then you would not point it anywhere. Config root option is already set to '' (empty), which means it will look in the same dir as where index.php exists, which is default (the location where you drop index.php, as explained in the docs).
Johnny91 I have put the /admin/ inside
websitename/public_html/_files/
That means you have a dir public_html/_files/admin, and if you want to point it to public_html, the same as your main index.php, you would set 'root' => '../../'.
Johnny91 the admin folder is inside _files/
I would not personally do it like this, but it depends on where your main root is (which you aren't telling me). I would rather create a dir _filesadmin directly in public_html, instead of adding it into _files, which is strictly meant for config and cache files.
