Hi,
There are two ways to create a new vendor. The first one is in the front-end, with the "vendor registration page".
The second one is in the backend, in "HikaMarket > Vendors", you would see the list of your vendors and there is a "New" button.
You can enter a name for the vendor and select the vendor administrator (A user from your HikaShop users).
A vendor is a new entity type and it's not a single user. It's more like a company which could handle several users into.
So, for the same vendor, you can have several users with different rights. For example, one user could just have rights to edit products and one user could just have rights to edit orders.
We are working on an HikaShop plugin which would create vendor while an HikaShop user is created. With it, it would be possible to have one vendor per user (and maybe with some options for groups limitation).
But I forgot to add the feature of "mass vendor creation". It's a good idea ! Thanks
Regards,
Jerome