Where?
Well in the port settings you need to put in your computers server IP address. This is what tells your router "This computer wants portforwarding service."
Easily find your server IP with the following:
1. Press Windows Key+R.
2. Type "cmd"
3. Then type "ipconfig", then *enter*.
4. Now look by IPv4, this is what your server IP is. (Ex: 192.168.1.4)
That IP should go into your port settings. Under "LAN Address", or "Server IP". (However your router works)