The sample includes a shopping cart feature which is for demonstration purposes only. Photos and products in the demonstration application are not actually for sale.
Keyboard commands are supported in the application for navigation purposes. The arrow keys can be used to select a photo. The tab key supports navigation to and from the various portions of the UI.
In order to crop a portion of an image, simply drag the mouse over a portion of the image while holding down the left mouse button. This will draw a yellow border around the selected portion of the image (the intended crop region). The Crop button will then be available to you.