This is definitely the wrong forum, but the mods should be able to move the thread intact.
So, I'm going to presume:
1.) you're trying to host from a home internet connection
2.) on your personal computer
3.) thats running some sort of Windows OS
4.) you have some sort of broadband connection and are using whatever router box your internet provider gave you
We will need to know the model # of your router to help you with explicit details. But in general you do the following:
1.) Open your router admin settings. The addresses for this are very often on of these:
2.) Get the MAC address for your PC's network adapter being used to connect to the router. A fast way to do this is
WIN Key + R -> Run the program
cmd ->
ipconfig /all
3.) Set up Static IP assignment by your routers DHCP so your PC always gets the same LAN IP, this is usually facilitated by MAC address, which you got from step 2.
4.) Open up the PortForwarding settings.
5.) Open up whatever ports your need to be routed to your PC