DNS Problem or hostname?

Hello my friends. I hope you can help me.

I'm new in WHM so I expect you have patience, please.

I have a dedicated server and have recently installed Centos 6.8 with Cpanel/WHM.

So let's go to the problem:

I have my ip X.X.X.X:2087 that I access my WHM (I don't know why I can access with my hostname, supposed to be "mywebhost.com", for example). So, I configured the new package, and added the new account for hosting with the example name of "mywebsite.com". But there is the problem. I don't know if I use the dns like "ns1.mywebsite.com" or "ns1.mywebhost.com". The IP of "mywebsite" can be the same that "mywebhost"? Because I don't know if ns1.mywebhost.com it's the same ip of X.X.X.X or have to be another IP, and the same to the "mywebsite". I hope you understand what I'm trying to say.

Thanks!