Port Forwarding Wizard is a very simple piece of port forwarding software that runs on OS X. It supports Snow Leopard, Lion and above.
The Port Forwarding Wizard for MAC communicate with router by using UPnP standard. So what you need to do is just enable UPnP option in your router.
When you launch Port Forwarding Wizard for MAC, it will auto detect your router. When your router is detected, the tool will fetch current port forwarding entries from router and display for you.
Then you can just simply click "add" button on gui, then pls fill in the port that you want to forward and internal ip address.
Anyway, It is very simple to use:)