You must have received information about your name server IPs for your reseller account.
Your provider must have provided their own white label nameservers and instructions on how to use provided IPs for creating your own NS on your own domain. With most of the registrar it is called child name servers or host name servers. With 1and1 it is a bit different method.
So the steps you have to take are.
1) Create your own nameservers using provided IPs at registrar.
2) Create your own nameservers entries on your hosting server ( your provider can help in this.)
3) Use the newly created NS for hosting domains.
Now with most of the registrars it's straight forward and simple to create your own NS, but with 1and1 a bit complex.
So visit the link below and see how to do that at 1and1
If you are unable to do that, ask your provider to help you out on this and if that fails you can get in touch with me and I will gladly help you to fix the issue.