If you want to import additional characteristics or characteristic values in HikaShop, you can import a CSV in the hikashop_characteristic table of HikaShop via your phpmyadmin.
For the structure of the CSV, you can export the data of that table as a CSV and then open it in Excel and complete it with what you need before importing it back.
But then, for the variants of the products, once the characteristics and their values are in the hikashop_characteristic table, you can reference them in your product CSV. Again, you can use a CSV exported in HikaShop for an example.