WordPress.org

1. Install and activate the plugin as usual.
2. Ensure the WP e-Commerce plugin is installed, and there is at least 1 (published) product in the store.
3. Go to Appearance - Widgets, and drag the "Featured Product" widget into a sidebar area and select a product from the drop-down.
4. If Random Product is selected, use the Category drop down to indicate whether the random product should be selected from any category, or if it should be restricted to a specific category.
5. Choose whether to show the product image or not.
6. If Show product image is selected, choose between the size options (Thumbnail Size, Full Size and Custom Size). Thumbnail Size refers to the WP e-Commerce setting Default Product Thumbnail Size available from the WP e-Commerce settings page. Custom Size allows the image size to be specified explicitly for the particular widget.

Note that there are no plugin-specific settings, all configuration is done via the widget itself.