Here's a way to your cPanel. Login here:
https://x10hosting.com/control/login.php. Click on Hosting at the top, and then look for the button that says "Login to cPanel". Click that, and then you should be in your cPanel.
Under the Files section, click File Manager. Choose Web Root and then click the Go button. You should be in the public_html directory of the File Manager now.
At the top, 5 options from the left is Upload. Click that. Then click browse to select your file from your computer. That should be it.