1. Prepare your slides to save as jpg files (just make sure you finished it).
2. Go to ribbon and click File.
3. Select Save as and next click twice on Computer
4. New window pops out. Write your File name (it will be a directory name not a file name).
5. Choose JPG extension in Save as type drop-down list.
6. PowerPoint asks you Which slides do you want to export. Click All Slides.
Tip: PNG is also a good extension for images.