An identificator is a unique identifier referring to an Imperial citizen. It's roughly equivalent to the 'username', 'handle', or 'name' that other systems use. YeempBBS currently requires an identificator to post, although it doesn't (yet) check to make sure that the identificator is valid or that the person posting is actually the owner of said identificator.
To get an identificator, apply for Imperial citizenship.
This is the default identificator-help file; the admin of this BBS may wish to change it to something other than Imperial propaganda.