If your domain is registered with GoDaddy, you can access your DNS Zone from your Domain Control Center → Domain settings → Manage DNS:
You can find a detailed guide on creating, editing, and deleting DNS records at GoDaddy here: Manage DNS records.
To connect a domain with your Hostinger services, use the following values:
mx1.hostinger.com (Priority: 5)
mx2.hostinger.com (Priority: 10)
If you encounter any difficulties managing the DNS Zone, make sure to contact GoDaddy support directly. Alternatively, you can transfer your domain to Hostinger, so you can manage your hosting and domain in a single place.