If you don't alread know your IP, "ping" it by server name.
Go to DOS (command prompt, or "cmd" in the Windows run window), and type "ping servername.com" and it should show the IP.
Note that I have ICMP (ping packets) response disabled, hence the timeouts.
But that not what matters here anyway. It still shows the IP.
It doesn't matter what you use -- same place.
The IP is simple bypassing nameservers (DNS), which is useful if NS isn't setup yet.
You can always add NS in your local computer HOSTS file. That's how I dev sites.
I would update NS as soon as you can.