Spawn for Multiverse Core Not Working?

So I recently just got Multiverse Core and I need to set a main spawn for my world. So when I type in the command "/mv set spawn" this message pops up: Multiverse Does not know about this world, only X, Y, and Z set. Please import it to set the spawn fully (Pitch/Yaws). I dont know what it means, so if someone could tell me what this means or fix this, then by all means please tell me! thank you