In the Create a store tab, you can directly create a store that will be attached to your WiziShop Partners account.
All you have to do is fill in the form displayed, with your customer's details.
The information entered will be automatically pre-filled in the store's back office.
The store you create is in unlimited test mode, giving you all the time you need to develop it.
Once the store has been created, you will have access as Shop Owner, and you can then create a user for your customer directly from the store back office to give him access.
To keep the store information in your store list, you'll need to keep your user as "Owner".