This cannot be done through the Bookvault platform and you would have to raise a support request via email.
Email our main support line at customers@bookvault.app and provide us with the current ISBN you have inputted, and the desired ISBN you wish to change it to.
PLEASE NOTE: If you have already set the ISBN up for distribution and/or made sales through our retail network, this can potentially be too late to change. You will also not be able to change your ISBN if there is a live order.