Q: I'm setting up airport for first time. I'm getting error no DNS servers help

DNS server is that translation from a website address in words meaningful to us.. eg www.google.com to an actual number that computers can use. Without DNS the internet may work but you would have to know the ipv4 address of every site you want to visit.

Whenever you don't know the meaning of a term just type wiki plus the term in google search.

http://en.wikipedia.org/wiki/Domain_Name_System

We cannot really help fix the problem without knowing a good deal more info.

So

What modem do you have.. make and model may be a help?

Who is your ISP.. may be helpful??

Is the modem also a router?

How is the TC connected to the modem?

How is the computer connected to the TC?

A primary example of where you get this problem is a pure cable modem.. ie has no router in it.

When you replace an existing computer or router that is plugged into it, with the TC, requires that you power cycle the modem. In some cases the off time is 5min.. for a lot of services, it needs to be off 20min.. and for some even longer.. maybe an hour or overnight.

But it is not worth getting into specifics without knowing the rest of the system.