Hah, well, nobody knows where you are, and it'll involve a little more than just typing in a server name when you want to add a service or host for Nagios to monitor. You'll actually have to learn Nagios if you want to be able to successfully modify and use it.
Anyways, the most we can do is help you based on your config errors...which you haven't posted. Post something. Give us something to work with here.