If you have a Shared Hosting account, you'll use the following Name Servers:
NS1.LITHIUMDNS.NET and NS2.LITHIUMDNS.NET
If you have a Reseller account, you'll use the following Name Servers or your private name servers:
NS1.LIPOWERED.NET and NS2.LIPOWERED.NET
If you have Windows Hosting, you will follow the instructions in your welcome email for your name server configuration.
VPS customers, your VPS is configured with DNS resolvers so it can connect to the internet and resolve DNS names, but if you intend to host DNS or manage DNS records, you'll need to use a 3rd party DNS provider or roll your own DNS server on the VPS. This is common with VPS and Dedicated Servers since you're typically managing your domain name elsewhere and just make the necessary A record change for your hostname to point to the VPS IP.