First you need to enable the server by going into Tools>Options>Player Client Server and checking enable. Make sure the port is 5000 (should be by default). Now you need to find out your external IP address. Easiest way is to go
to http://www.ipchicken.com. Copy that ip address down because you will need it to test the server.
Do a google search on your router to find out the network address. It should looks something like 192.168.0.1 (it is different for different
brands and types. Type that into your address bar of your browser(what you use
to surf the internet). You should see a login screen for your router controls.
Enter in the login you put in during its setup. Username: and Password: If you
do not know it you should find the person who put it in or try doing a hard
reset. You need to forward the port for the server now. Navigate the the
advanced page and then the Port Forwarding tab. Application name: Player Client.
IP Address: (you need to find the computers network ip located in the
setup/network tab). Some routers let you use a computer name(the name you gave
your computer) but not all of them do. You need to know that no 2 computers can
use the same port, so you need to make sure that no other computers are useing
port 5000(or you need to change ALL settings to a different port). Hope this
rough guide will help you get your players connected. The test you can preform
is to take the IP address I told you to copy, and put it in the address of the
Player client window. If your port is not properly configured it will not
connect.