On the Create or Update form for the owning group, select the required vault from the drop-down list. An owning group can be related to only one vault, but many owning groups can be related to the same vault. When a file is attached to an object that is owned by the owning group, it will be transferred to this vault.
If the owning group of the object is changed to one with a different vault, then the file is transferred to the new vault.