Hi,
There is nothing to import user information because the user information needs to be attached to a user account and the user account system is handled by Joomla, not HikaShop.
So what you can do already is import user accounts in your Joomla with an extension like that:
extensions.joomla.org/tags/users-import-export
Then, you can install HikaShop again and it will run the user synchronization so that you see the users in the Customers menu of HikaShop.
Then, if you want to import the address data of the customers, you would have to have a custom script and/or do it via your phpmyadmin in the hikashop_address table. If you're not a developer, it won't be easy.