Hi Media X/Anshu, many thanks for replying. But I think this may be the root cause of why I can't find an answer – as all queries (& answers) I find, relate to uploading files to a WP theme on a hosted server via FTP etc. I do not have a hosting provider to do anything on my behalf.
My personal query is based on me using a Mac with XAMPP as the local host. Is FTP involved here? I read the "Using an FTP Client" multiple times - I just do not understand where to go to actually see the items in that screen grab. Is it in the WP folder that is in the XAMPP folder? or is it e.g. within http://localhost/phpmyadmin/? Also, I cannot right click on a index.php (in WP/XAMPP) as I use a Mac - so there is no pop-up function.