I know how to make the signs to join. I know how to save the arena. I don't know how to set it. How wolud I set the arena so people can join it??
@MemeplexOwner what timtower say's is a more proper way then my suggestion so if you can hook the world edit api that would be the best solution. Another way is by just setting serveral spawnpoints and use a plugin like World guard to prevent building or block breaking in and on the arena.
Oh i can just check if they broke a block and then e.setCancelled(true); but I would prefer timtower's idea. Thank you all!