WooCommerce is the most popular e-commerce plugin for WordPress. Now you can have a shop with all e-commerce features on WordPress.
Before you start adding products, please go through the WooCommerce plugin settings and specify everything you need for your site.
Go to WooCommerce > Settings > Products > Display
To set up the display of the Single Product Image and Thumbnails sizes go to Shop page > Customize > Woocommerce > Product Images:
Adding the products: You can easily add new products via Products > Add Product
Just specify all the details with the description and shipping details. For a single product, you can upload several photos in Product Gallery. More information about the WooCommerce features you can find here: http://docs.woothemes.com/documentation/plugins/woocommerce/getting-started/