If your domain is registered with SiteGround, you can access your DNS Zone from your Client Area → Services → Domains→ Manage.
You can find detailed tutorials on creating, editing, and deleting DNS records at SiteGround here:
Hostinger default DNS records:
If you face any difficulties while managing DNS Zone at your domain provider, it’s best to contact SiteGround directly. Alternatively, you can transfer your domain to Hostinger so your hosting and domain will be managed from one place 😊