iCloud: Add photos to My Photo Stream
You can manually add photos from iPhoto, Aperture, or the Windows desktop to My Photo Stream. For example, you can add photos you took on your iOS device or imported on your computer while My Photo Stream was turned off.
On a Mac using iPhoto or Aperture
For instructions, see one of these iPhoto Help or Aperture Help topics:
On your Windows computer
Select iCloud Photos under Favorites in a folder window of File Explorer (Windows 8) or Windows Explorer (Windows 7).
Double-click My Photo Stream.
Click “Add photos” in the toolbar, select one or more photos to add, then click Open.
For a list of file types that can be added to My Photo Stream, see the Apple Support article iCloud: My Photo Stream FAQ and see “What photo formats does Photo Stream support?”