In order to be visible from the Internet, you will need an entry in your company's DNS server and possibly a firewall hole. For the domain name, you will want to put something like example.com. For instance, www is the hostname of the web server, and example.com would be the domain. This gives you a fully qualified domain name of http://www.example.com.
If you can use DHCP it should set up everything correctly. If you have to configure it manually ask your network admins for what to put in. Unless your company does not use DNS at all there will be a domain name which you should use, too.