Simple question about Setup

Hello, im going to setup virtualmin to my server but im not sure what is it asking by saying “Fully qualified host name”.
I wrote ns1.mysite.com and it didnt work.

I bought domain from godaddy. Should I process extra steps from godaddy?

EDIT: Okay I figured it out. It just asking the main domain name like www.mywebsite.com or mywebsite.com.
I confused when read “Example: host.domainname.com