open up a web browser and type in the ip address of your router then log in and look into the advanced setting, there should be something called port forwarding, put the port number you want to open in their follow with your machine's ip address
to check your ip address and your router's ip address, go to start->run->type in "cmd" to open up the dos window, then type in "ipconfig" and press enter
ip address = your machine's ip address
default gateway = your router's ip address