Add a root to an Internal DNS server

[Soraya Hassanaly]

Hi All, 
I have an Internal DNS, which I was said seemed to work without any root
configured on it. 
The current internal domain is xxxx.net. If I want to add another domain  -
yyyy.org - and make some delegation for it, I think I have to add the root
domain and then configure the delegation.


But how do I add the root domain in the DNS,? 
What are the impacts? 

Many thanks

Cheers