To enable the slideshow mode simply press the S key. This will display all your images switching from one image to the next automatically after some delay. During a slideshow, an icon appears in the upper right corner of the screen.
You can change some options by going to the Slideshow tab of the Options dialog. You can change the delay between images, set the random order... You can also pick your favorite MP3 file and have cam2pc play it during the slideshow!