All new web hosting plans have a place holder page to show the website is working. You'll need to remove this page before you can add new files to your website. To do this, simply enter your cPanel and click "File Manager". Then navigate to the public_html folder where you will see an index.php file. Click that file and choose the delete option.
If you add a script like WordPress with our app installer it will ask you to remove the index page. Just click yes and it will do it for you.