Do you mean a tutorial for making a slideshow by importing photos onto the timeline in MEP? If so then this is as simple as importing your photos onto the timeline, then adding transitions, effects, etc. See the first part of the manual. Remember, a slideshow always ends up as a video.
Or do you mean a tutorial for using Slideshow Maker, one of the wizards in MEP? If so, then so far as I know, Magix did not create one for their site. They have many tutorials, including Soundtrack Maker, but not Slideshow Maker for some reason. It is actually quite intuitive. Look in the manual and follow along on the screens. You have to learn by doing. Start with only a dozen images or so. You won't break anything. You will see where the slideshow ends up and then you can look at modifying the result on the timeline. Also, you may have a manual for Slideshow Maker 2. Look for a pdf file called SlideshowMaker_EN in the following folder if the folder exists: