Turky_Knight, welcome. Glad to hear you are interested in playing YB! I would suggest going to this site where you can read the rules first: YB rules and generator
Check out the rules and the advancement info, then make up a name for your fighter who will start as a white belt. Once the rest of the people playing are over on this new board (which will be soon once I tell them it's up!) then you can try to find someone to fight against using the generator to get random attack moves. Maybe read a thread or two of others fights first if you want to see how it works better before jumping in, or just take the plunge. Ask questions if you have them, most people will take the time to answer you well.
Be aware also that there are two different games mostly played here in the Fight Club. YB is the first and you have the link to that. There is also YB Adventure (or YBA) and it has many similar things but a different rules page which can be found in the 'Useful Threads' thread on this new board here in the Fight Club. Both games are fun so check them out and I hope you stick around to play and enjoy!
Welcome to YB! Have fun. I believe that there are a couple other relatively new players around. You can either start up a thread and challenge other white belts to battle in it, or wait around and look for someone to fight.
I'd also like to mention YBA. It's an offshoot of YB, and pretty fun, IMO. You might want to look into it.