Just register the remote SQL Server in the Enterprise Manager and start administering it, just as you would administer a local server.
If the SQL Server is across a WAN/Internet, then you will have to connect using the IP address of the SQL Server. In that case you might have to add a TCP/IP advanced entry on your client PC using the 'Client Network Utility' (Start -> Programs -> Microsoft SQL Server -> Client Network Utility). You'll find the following article helpful:
http://www.verio.net/support/view_ar...fm?doc_id=3851