‘To post on a Local talk board, you must have a Local nickname. This can either be the same as your current nickname, or a completely new one. You only need to set this once. It won't be changed after that.’
I think this means you already have a local nickname.
The new local forums have been incorporated as a subject on the main forum and so show up on the Active list. I kept the same name on both but some people didn't. I think GNHQ are still perfecting the changes.