It's as easy as dragging them into the timeline! If you go to 'Program settings' >> 'Video/Audio' tab you can set the standard picture length to a single frame (two or more frames may still give reasonably smooth animation) rather than making adjustments later. Note that if you bring in a group if objects the order in the timeline will follow whatever sort mode is currently in effect in the medial pool / explorer window. Also alpha sort requires leading zeros to keep 000300.jpg ahead of 002000.jpg.
Depending on your program version and computer specs there is likely a practical limit to the number of images you can use. A workaround is a utility like 'VirtualDub' to frame-serve the images. You load your stills and save-as a dummy file to start. The dummy file is then used in MEP as if t were video. Alwyn, a regular contributor on the other Magix forum http://support2.magix.net/boards/magix/index.php?showforum=113, has a tutorial here: http://www.aaproductions.net/mep/index.htm . It was written about dealing with audio sync issues for video so just ignore anything about de-muxinging etc.