To design your image recognition system, you need to specify the concepts that you want to recognize. You can do so by clicking on Add a concept. You need to give a name to your new concept, and you can add a description, which can be convenient to explain to the annotators the corresponding concept.
The list of concepts that are attached to a project is displayed on the navigation bar.
By clicking on any of those concepts, you will access a gallery view with all images checked for that concept. See Visualizing Images to know more on the gallery views.