Baires, unlike other programs does not let you to select images for resizing. It resizes all images he finds in Source directory. It is designed to resize many images in quickest and simplest way possible.
This is particulary useful if you use same directories often, like, for example, resizing images from your digital camera, to your directory for resized images.
Since it saves last used parameters, usually one click is enough to do the job. Can't get simpler than that.