You will need to change your current domain's name server to:
If you have reseller hosting with us please follow the instructions regarding nameservers in your Welcome/Signup email sent during registration.
This can either be done via your domain registrar control panel.
As long as we support your TLD (.com/.net) bit you can also transfer your domain to us and our systems will automatically update everything for you.
This also means you pay one company for your Web Hosting and Domain Registration.