If you don't know what Port Forwarding is yet, you might want to start by reading our What is Port Forwarding guide.
You might also be interested in our huge collection of Router Screenshots where you can see every page of every router that we know of.
To setup port forwarding on the Apple AirPortExtreme router your computer needs to have a static IP address. You should complete one of the following steps first:
Now that you have setup a Static IP Address on your computer, please enter the IP address that you assigned to your computer here:
Open up the finder on your Mac.
Click the Applications button near the left of the page.
Click the Utilities button near the right of the page.
Click the AirPort Admin Utility button near the right of the page.
Select Apple Base Station from the Select Base Station list.
Click the Port Mapping button near the top of the page.
Click the Add button near the right of the page.
Enter the port to forward into the Public Port and the Private Port boxes.
Enter the ip address to forward these ports to into the Private Address box. If you are forwarding ports so you can run a program on your computer, you should enter your computer's ip address into that box.
When you are finished, click the Ok button.
When you're finished, click Update near the bottom of the screen to save your changes.
And that's it! You're done!
Now that you have forwarded ports for any port on the Apple AirPortExtreme you should test to see if your ports are forwarded correctly.