You are supposed to have 2 name servers in your case they would be something like
ns1.bluehost.com and ns2.bluehost.com It takes around 24 to 36 hours for the DNS to propogate all over the internet. How will you know when its done? well just type in the domain name in your browser if it takes you to your site then it has propogated. You dont have to do anything else, rest of the headache is that of your host.
He said he changed it for both :)
Your webhosting company will know what your domain name is and what the IP of your server is.
You tell the domain registrar what the name server of your webhosting company is. :)
So when someone wants to get to your site ...
They go to domain name
They end up at registrar
Registrar points them to your hosting company's name server
Hosting company's name server tells IP address of your machine
You end up at your machine :)
Approximately it takes 24-72 hours to register and transfer domains.