N.B: first enable the multi vendor mode in the general VM config
read this first:
https://docs.virtuemart.net/manual/general-concepts/211-multivendor.html1. if the user is not already registered create them in the Joomla Users and assign them to your "chosen" Joomla User group - e.g. manager
2. Open them in the VM shoppers dialog and fill in the required fields
3.
Save and close and then in the Shopper over view dialog assign them as a Vendor via the checkbox and "Is A Vendor" button
4. Now reopen them the VM Shoppers ( click again on the username) - they will now have a Vendors tab - assign a name etc and the vendor entry is then created