Problems with network configurations

[newbiepg]

I am having problems getting my computer in the network
I am running redhat 7.3 , this shows in the network only if I search with an ipaddress

Either the name is absent or it is shown as localhost

My questions are
How do I change the name of the computer?
How do I put it in the network so that it is visible to everyone?
We have an NT server

Secondly when I put valid users = server(or anything else)

The computer is asking for a username and password, now it does not work for any username and password combination here

Thanks you all