You can easily disable directory listing by logging in to your cPanel and navigating to the Indexes:

Once there, locate the public_html folder, select click on Edit next to it and choose No indexing on the next page. Next, save the changes:

You can also upload an empty index.html or index.php file if you don’t want the content to be displayed on your website (while still disabling the list of directories). Alternatively, you can add a few lines of code to your .htaccess file defining which file should be meant for the first page of your website:

Replacing newpage.html with your index file name.