As Producer camera do not appear in the Viewer window, you cannot click a wireframe model to select it, as you would with a Custom camera. 
There are two ways you can select a Producer camera: in the Scene browser, or in the Viewer window View menu. 
Scene browser
- Expand the cameras folder in the Scene browser. 
 
- Double-click any of the seven Producer cameras to display its camera settings in the Navigator and Properties windows. 
 
- Right-click any of the seven Producer cameras and select Make Camera Current from the context menu. 
 
 
View menu
- Expand the View menu in the upper corner of the Viewer window. 
 
- Expand the Orthographic menu and select the Producer camera you want to use.