To set up an emulated IPX connection over a LAN or the Internet, you must first choose which computer will act as the server and determine what its IP (external, if you're trying to connect over the Internet) is. If you require port forwarding, the server listens on the default UDP port 213.
Now, both players should launch the "Start Menu/Programs/GOG.com/[Game_Title]/Multiplayer" shortcut.
The server should select 'Start Network Host Game' and wait for the client.
The client should select 'Start Network Client Game' and input the host's IP address. If the address is correct, and the host is running the game in Host mode, then the connection should be established almost immediately. If you encounter errors, please check the IP address and try again.
An emulated IPX connection should now be established and both computers should be able to "see" each other in-game.