How to upload to the cPanel my non-worpress site

If you want it to be seperate from all the others, you need to create another sub-domain (addondomain4.com), which will create another directory (folder) and upload it to there.

u create three addon domains and automatically three subdomains are created???

Yes, cPanel works that way. for every add-on domain, a corresponding sub-domain is created off the main domain. So if you have example.com and you add on newsite.com you’d have a sub-domain of newsite.example.com set up as well.

Just as a note this is all cPanel, and really has nothing to do with WordPress. 🙂

creating a website with one of them, then we automatically have the same website with the rest one, too??

Yes. The same content is served on both.

And about my index.html… we finally throw index.html with its folders(css,js,etc) in the automatically created directory of the new addon or subdomain?

Yes. There’s only one folder that is used for both.

Sub-domain looks like this > subdomain.mainsite.com.

It is sort-of a “stand-alone” site connected to the main site, but it is outside the main site. A sub-domain is treated by the search engines as a truly unique website.

Sub-directory looks like this > mainsite.com/subdirectory
A subdirectory is inside the main site. A sub-directory is treated by the search engines as a part of the main website.

Now, here’s the confusing part for some people…
When you look at your files with File Manager or a FTP client (…like Filezilla) your subdomains are “folders” inside the public_html along with your wp-admin, wp-content, wp-includes and the other single files that make up WordPress.
So… you may think that they are inside the WordPress install, but they aren’t.

If I went through my cPanel File Manager or through my FTP client and created a directory (folder) named “images” and put some images in it, this would be a subdirectory that I could call images from with HTML or PHP, but it could not run anything by itself, it’s just a place to hold files – or jQuery plugins, or fonts, or whatever.

While a sub-domain looks like another folder or directory within your web site file structure, there is actually a little more to it.

Unlike sub-directories, sub-domains MUST be created in the cPanel under the SUBDOMAINS link (not the File Manager). When the server creates the sub-domain based on the name you provide thru the cPanel interface, it also creates a cgi-bin folder just for that sub-domain, then creates a folder for the subdomain and places it within your public_html folder.

The sub-domain can run it’s own cgi scripts just as if it were a web site on it’s own.

So, to run properly, your HTML files with their own index.html, css folder, etc. should be a subdomain, not a subdirectory.