Port Forwarding simply tells the router which computer on the local area network to send the data to. When you have port forwarding rules set up, your router takes the data off of the external IP address:port number and sends that data to an internal IP address:port number.
1. Open the terminal under windows (Win+R->cmd), and run
ipconfig2. Note down the IP Address of Ethernet adapter Local Area Connection.

3. Open the browser, go to
192.168.1.1
and log in.4. Go to Advanced Setup->NAT->DMZ Host. This depends on the type of router. Anyway there will be a NAT option somewhere.

5. Enter the noted down IP Address from step 2 here.

6. Press Save/Apply.