Chaos: You have to be a paying member to play in ponds, there are public ponds and fellowship only ponds.
Just like the other sites, there are "perks" for being a paid member.
As far as understanding ponds, perhaps it might be better to look at a finished pond move for move, here is one you can look at http://brainking.com/en/Pond?bms=0&g=4630 , You might just recognize the winner!;-)