On this tab you can create zones and DNS records for your domains.
You can either do this by using the DNS Wizard which will automatically create a set of common DNS records for your domain (like www, mail, ns records, etc.), or you create the zones and records manually under DNS > DNS > Zones - you will also have to go there if you want to create further DNS records that are not created by the DNS Wizard.
Normally, when you purchase a hosting package, DNS records are automatically configured.