ID:2042766
 
When i try to host my own game it says the follow;

BYOND hub reports port 54121 cannot be reached by players.

A firewall or router may be interfering with your connection. For information on hosting worlds through a firewall or router, please visit BYOND Help or portforward.com.

Stopped server

What must i do to fix this !! is it for sure my firewall?
It's exactly what it says it is, it's either a software firewall, hardware port blocking on your router, or both. There's no way to really know your network setup to be sure, it's more than likely a combination of Windows Firewall and port blocking on your router/modem.
Could some kind soul give a step-by-step guide to solve this issue please?
Forward the ports on your router. This will help: http://portforward.com/

Once you forward your port, host the game with the port you opened. Problem solved.

I should also add that SOME Internet Service Providers block ports and even hosting so even if you do open a port, your ISP will still stop you. In that case, you'll need someone else to host for you.
In some cases depending on your router, you may need to create a static IP address. You can find guides on how to do that with a simple google search. I hope that helps!