Read http://www.shopbop.com/go/widgets, a summary of which follows:
- Install the plugin from within the WordPress Dashboard
- Activate the plugin through the 'Plugins' menu in WordPress
- Enter an email address to which a registration email will be sent
- Click on the activate link on the registration email
- Edit your preferences in the ‘Shopbop’ settings panel
- Drag and drop the widget onto your sidebar. Go to 'Appearance' then 'Widgets'