Where to add host headers

[lemore]

I'm moving my hosted website's to my own VPS with Cpanel/WHM.
Because my website is still live on the old host, i've added beta.newsite.com in the DNS on the old host (a-record to new host IP). Then i've setup the website on the new host, but how can i direct the beta.newsite.com to the correct NEW site in WHM/Cpanel on my own VPS host/ip?

I tried the domain tools of Cpanel but i can't get that to work.
Sub domains look the way, but then i have to choose a document root, but that just has to be the domain root, and if i try that it gives me the error: You do not have permission to create subdomains of the server’s hostname.

What am i doing wrong?

 

[dalem]

go to tweak settings on your VPS server
"Allow resellers to create accounts with subdomains of the server’s hostname."
and check on

 

[cPanelMichael]

Hello

In addition to the previous post, please also ensure that your server's hostname does not match the actual domain name of the account. Instead, ensure it's something such as "server.domain.com".

Thank you.