From Official Wiki of the Renaissance Kingdoms

A Hall is a sub-forum of the county Inn forums, on Forum 1, where all the roleplays that take place in a village are posted, so each Inn includes multiple Halls (one for each village in the county).

It is only possible to post in a particular Hall if your character is actually in the village in question. The ability to read and post in town and county forums on Forum 1 is limited by the location of your character in the world (see forum for a more detailed explanation).