You have to install iCloud Control Panel from apple.com
If you already do, then click the Start menu in the lower left corner of your Desktop
Control Panel> Network and Internet> iCloud
Click on Photo Stream so there is a checkmark in the box.
Click "Options"
There will be a path to your upload and download photos from Photo Stream.
may have to change the location to make them show. I'm sure you know how to do that tho.