The same way you find a way home. How does that work? Presumably only if we assume the context of a particular collection of physical worlds (perhaps with selected preferred approximate location). Given that we're considering only some worlds, additional information that an agent has allows it to find a location within these worlds, without knowing the definition of those worlds.

This I think is an important point, and it comes up frequently for various reasons: to usefully act or reason, an agent doesn't have to "personally" understand what's going on, there may be "external" assumptions that enable an agent to act within them without having access to them.