Once the demo data has been imported, you will have to set WooCommerce with the Setup Wizard. Click somewhere in you WordPress dashboard, you will be redirected to the Wizard. Follow the steps to install WooCommere correctly.
Optional: Import WooCommerce Sample Products
Click Products > All Products > Start Import
Download WooCommerce and unzip the folder. In the WooCommerce folder open sample-data > sample_products.csv > Import > Scroll down and click Run the importer. The import process may take a few seconds.
Fore more info see: