In order to connect to a remote server, you either need to have a fully qualified domain name (FQDN) for the server (e.g., sql.domain.com) or the IP address of the server.
As previously mentioned, the remote server must not be firewalled against port 1444, or you must set up the firewall to forward incoming port 1444 requests to the appropriate remote server.
Additionally, the remote server must be configured to allow remote connections via TCP / IP. See here:
http://nil.checksite.co.uk/index.cfm/2007/4/30/SQL-Server-2005-TCPIP-Connections
Once your remote server is configured properly, in SQL Management Console, create a new connection:
Provide the FQDN / IP address to the server in the Server Name field. Do NOT provide a protocol (e.g., http); provide only the domain name or IP address, e.g., 127.0.0.1 or sql.domain.com
Under Authentication, choose the appropriate authentication method.
If you are using Windows Authentication, you must provide a domain and user Domain\Username combination ON THE REMOTE SERVER / NETWORK that has permission for the DB objects.
For example, if the remote SQL Server box is named SQL and you want to log in as the built-in Administrator account on that box, you would use SQL\Administrator as the user name and supply the admin password as password.
If you want to connect via their NT Domain, you would provide the name of the domain and user name, of course; and that user name would need permission on the SQL Server to use the objects you want to access remotely.