Beeright,
Was moths are the clean up crew. They do not take over unless the hive is very weak, usually after the bees have moved out. Sometimes they will take over areas of the hive that the bees are not able to protect because they have too much space especially with old drawn comb.
Add the next super when they have drawn out and started to fill 8 of the ten frames, the box is full of bees and you have a flow on.
Jim Altmiller