Before using a domain with your hosting account, it has to point to the appropriate nameservers :)
To find out which nameservers your domain should point to, simply locate the Details menu in your hosting account's hPanel's section Accounts and check the Nameservers details section:
Hostinger nameserver details:
- Your domain's nameservers can only be set from your Domain Name Registrars side. Notice that some registrars allow their domains to be pointed ONLY via A Record. You can check this tutorial to guide you through the process.
- Changes to your domain's nameservers will need 24-48 hours to fully propagate worldwide. Your website may experience issues during this period.