Most of the time you get your DNS servers ip through DHCP in well configured network.But if you want to override the dns servers, it can be achieved by performing the steps below.
Open the file
sudo vim /etc/resolvconf/resolv.conf.d/base
Add the servers like below
nameserver 8.8.8.8
nameserver 8.8.4.4
Now update with resolvconf
sudo resolvconf -u
palatana 