The index/default page for new, empty accounts is a CGI script (a program) that is invoked when there is no content in the public_html folder (or www "folder", which is an alias for public_html). You don't need to clear anything out, just add your content to the public_html folder. (By the way, that's pretty standard. The "default installation" in some places uses an index.php file that tells the whole world how to hack the system. That's great for a local WAMP or XAMPP installation, but not for a publicly accessible web server.)
The default page can be "sticky", though -- it can remain in your browser's cache (or your ISP's proxy cache), preventing you from seeing your own index page. You can clear your browser's cache and history then restart your browser before visiting your site to clear the problem on your end. If your ISP is caching the page, you may have to wait up to 24 hours for that cache to be cleared. (ISP caching isn't something you can fix, or something that can be easily fixed at x10Hosting's end.)