It is the name of the host server. It translates domain names into IP addresses.
It makes it possible for a user to access a website by typing in the domain name instead of the website's actual IP address. The form looks like this -> ns1.hostname.com.(It is just an example)
Go to My Account > My domains > At the right of your domain Click "configure" > Input NAME SERVER of your hosting registrar and click save.
After configuring NAME SERVER in Qi.fi, you should add your Qi.fi domain to the hosting registrar. It might take up to 48 hours for name server changes to take effect and fully propagate throughout the Internet.