This page means that your domain was successfully added to the hosting plan, points to Hostinger, and you can start developing your website.
Before moving on to create your website, open Websites → Manage, search for File Manager on the sidebar and click on it:
There, open public_html. Right-click on the default.php file (it should be the only file present) and choose Delete:
That's it! Now you can start a website hosting journey, for that you can either: