Open a web browser like internet explorer or Netscape.

Enter the ip address of your router in the address bar of your browser. In the picture above the address bar has http://www.google.com in it. Just replace all of that with the ip address of your router. By default the ip address should be set to 192.168.123.254.

You should see a box prompting you for your username and password. Enter your username and password now. By default the username is , and the password is admin. Click the Ok button to log in to your router.

Click Special AP on the left hand menu. This will bring you into the Special Application menu, where port triggering is done.

The ports required to setup port triggering will be specified by the software you are trying to use. Enter the trigger port in one of the Trigger boxes. Enter all of the ports that the application will use in the Incoming ports box. These are ports that the software's server will try to use when connecting to your machine. You can enter these ports in a list like (123,400,500), a series like (400-500), or any combination of the two(213,545,600-800).
Alternatively you can select one of the Popular applications from the drop down list at the bottom of your screen. After selecting an application, select an id to copy that configuration to. Once you have both of these selected click the Copy To button. You should now see a new configuration in the list above.

When you have finished adding triggers, click Save at the bottom of the browser window.

And that's it! You're done!