Trying to set Fiddler as a Reverse Proxy

I have been trying to set Fiddler as a Reverse Proxy, I've been following these instructions, but I just don't understand the point 3.

Option #1: Configure Fiddler as a Reverse-Proxy
Fiddler can be configured so that any traffic sent to http://127.0.0.1:8888 is automatically sent to a different port on the same machine. To set this configuration:

1. Start REGEDIT
2. Create a new DWORD named ReverseProxyForPort inside HKCU\SOFTWARE\Microsoft\Fiddler2.
3. Set the DWORD to the local port you'd like to re-route inbound traffic to (generally port 80 for a standard HTTP server)
4. Restart Fiddler
5. Navigate your browser to http://127.0.0.1:8888

How can I set the DWORD to the local port??? Sorry Im novice in network connections, please hope some good fellaw could explain step by step how can I do that. Do I have to do it inside Fiddler? Do I have to do it in windows? Im using windows8.1

PD: I know Im missing that step, cuz after doing steps 4 and 5 I get this message in the browser: "[Fiddler] The connection to '127.0.0.1' failed.
Error: ConnectionRefused (0x274d).
System.Net.Sockets.SocketException No connection could be made because the target machine actively refused it 127.0.0.1:8888"

EDIT>

When I set on fiddler>Fiddler Options>Connections>Fiddler listens on port: 8888
I get the same message, but instead of 127.0.0.1:8888 now I get 127.0.0.1:80

[Fiddler] The connection to 'localhost' failed.
Error: ConnectionRefused (0x274d).
System.Net.Sockets.SocketException No connection could be made because the target machine actively refused it 127.0.0.1:80

I have notice that in fiddler set reverse proxy page, it says…
Configure Fiddler as Reverse Proxy:
To use this method, the hostname for the request to reroute must be 127.0.0.1:8888, localhost:8888, [::1]:8888, or the machine's NETBIOS hostname on port 8888.

Is perhaps that why I can't get it to work? how can I set my machine NETBIOS hostname on port 8888?