Before using a domain with your hosting account, it has to point to the Hostinger nameservers. Hostinger nameservers are:
You can always see actual Nameservers in your Dashboard if you navigate to the Details section:
It is enough to set only nameservers values if the IP addresses are not required by your Domain name registrar.
Changes to your domain's nameservers will need 24-48 hours to fully propagate worldwide. Your website may be unavailable during this period.
Your domain's nameservers can only be set from your Domain Name Registrar side (the place where you purchased the domain). If your registrar doesn’t allow nameservers change, you can still point a domain with an A record.