If you've started creating your website with Hostinger Website Builder and wish like to use WordPress (or another CMS) instead, you need to delete the builder-based website and set up a new website from scratch using another CMS.
NOTES
A deleted website cannot be restored; all its content is lost permanently
If you have an email service set up for your domain, make sure to create a backup of your emails, as deleting the website will also delete emails
Navigate to the Websites section of hPanel and delete the website that you've created:
Then, add a new website to your hosting plan and choose WordPress (or another CMS) as your preferred website-building platform. If you select WordPress, to finish the setup, create a WordPress account, choose the preferred plugins and website template, and insert the domain name that you've previously released by deleting the website built with Hostinger Website Builder.