If you can see this page, that mean your domain is well pointed with the server.
This file is located in, cPanel > File Manager > public_html/index.html. You can simply delete this Sample index.html page.
There you can simply install our FREE SSL into your server. After you install SSL, simply you can put a redirection to https as default.
Install SSL Redirect to HTTPSWe have Astra Pro theme's Agency License so we can provide Astra Pro Premium Theme for a very low cost for lifetime. They have 230+ Premium Amazing layout collection too. You can see them all here. (Amazing Premium Layout Collection 230+.)
If you like to have Astra Pro Lifetime activation with Product Updates, here you can buy Astra Pro Theme.