If you are using Fedora 20 with the pre-installed GNOME environment, equals to GNOME network manager.
Search and find network connection application and open it. Then, find your connection in the list and click edit. Go to ipv4 settings select Automatic (DHCP) addresses only as method and write manually the DNS servers you want. Here we are using Google OpenDNS servers 8.8.8.8 and 8.8.8.4 , you can add mutiple addresses by separating them with a comma.
After you save the changes, restart network manager.
sudo systemctl restart NetworkManager
Now if you look at resolv.conf, you should see only the DNS addresses you added.
cat /etc/resolv.conf