No matter how many times I have installed and configured Linux, I can never remember the name of the configuration file that stores the DNS/Nameserver details.  This really only applies if your Linux machine is using a static IP address.  In most scenarios, it does not apply to DHCP clients.

DNS server settings are stored in /etc/resolve.conf  To edit this file, enter the following command from the shell
$sudo nano /etc/resolv.conf
(If you have installed XWindows/Gnome, you can use sudo gedit /etc/resolve.conf instead)

Add the entries for your DNS or nameservers as follows

nameserver <IP address of DNS server 1>
nameserver <IP address of DNS server 2>

etc…