If you go to "file" and click "save as", when the menu comes up, look for the file type, it will likely say "power point" or something to that effect and have a drop down box to choose a different file type.
Choose "JPEG" to save it as an image file and then your computer should save every slide as a JPEG image or "yourpicture.jpg" the only thing left to do is use a simple photo editing tool to crop the edges if you don't want the slide part in there, or just upload as is.