Quite problematic topic.
Ok, whenever you start the server, you dont need to do much additionally.
But whenever you start the client, you need to give the IP-Adress of the server as a parameter.
in the client bat : myprogram.exe -cl -ip 194.143.60.32
you need to find out the servers ip adress,
you could visit
http://myip.dk/ for example, to see what the servers ip is.
(dont mix this up with the local IP of the server behind a router!)
If you use a router, you might need to open certain ports, and forward it to the server.
(not trivial after all)
Setting up an internetconnection can be a pain, and very unsecure if you
just open up all ports.