Change nameservers for a domain in register.it

Domains and Products > yourdomain.com > Domains and Association > DNS Domain settings > Start the DNS modification > Change the DNS (accept the confirmation) > Custom configuration

New Location to access Nameserver change for register.it:

Login > Manage your Domains and Product > Domain and DNS > DNS Configuration > DNS Domain Settings > Start the DNS modification > Edit DNS > Yes I want to change DNS >