Not sure what the names servers are for your website's domain name?
Kindly refer to the welcome email sent to you after sign up. If you have lost your welcome email, you may request it again via email to firstname.lastname@example.org
The name servers listed in your welcome email will be the ones to use for all of your sites hosted on your account.
If you are a Reseller, then you can opt to use private name servers. If you are a Dedicated server owner, you must use private name servers.