Could not contact DNS server

Hello,
I’ve been having trouble connecting to the internet on RiscOS Pi. I have scoured the forums and the internet but have not found anything useful.
When I try to use NetSurf browser or just the internet in general, it always saya something like:
‘Could not resolve host: www.google.com (Could not contact DNS server)’
I understand that I have to do something in the internet configuration panel regarding a DNS address in the ‘Host names’ window but I don’t know what to put into the ‘Local domain’, Primary, secondary and tertiary ‘name server’ boxes. I have the Pi connected to my router with an Ethernet cable. I am also using the RiscOS image from the Raspberry Pi download page rather than the one from NOOBS as I have heard that that one has problems.
Thankyou if you can help.
Thomas.

The first question: Are you using DHCP or are you configuring manually?