WooCommerce is a WordPress plugin that gives you the power to add an e-commerce store to your site.
You can download WooCommerce from the WordPress plugin repository, or directly inside your site admin by searching for WooCommerce.
Once activated you will be given prompts to set up your store and then be given access to add products to your site.
If you are developing locally then they have some WooCommerce demo content you can use as a starting point.
For new users, WooCommerce has a complete Getting Started guide.
Unfortunately we don't offer customer support for WooCommerce. Since it's such a big plugin there's too much there for us to help with, however they have extensive documentation and a dedicated support team for you to get help from.
We'd love to get some feedback to help us create better themes.