Copied from: iCloud: Photo Stream FAQ
When you enable Photo Stream on your devices, all new photos you take or import to those devices will be automatically added to your Photo Stream.
On an iOS device, new photos you take will be automatically uploaded to your Photo Stream when you leave the Camera app and are connected to Wi-Fi. Note: Photo Stream does not push photos over cellular connections.
On your Mac, any new photos you import to iPhoto or Aperture will begin uploading automatically when you have a Wi-Fi or Ethernet connection. Or, you can change your iPhoto or Aperture preferences so that only photos you drag to Photo Stream are uploaded.
On a PC, simply drag photos to the designated Photo Stream upload folder. By default, this folder is located atC:\Users\Apple\Pictures\Photo Stream\Uploads. You can change this location by visiting Photo Stream Options in the iCloud Control Panel for Windows.
Transferring photos without iCloud to your PC is described here:
iTunes saves the photos from the camera roll inside the backup, but you can't edit, save or view them from within the backup.
Message was edited by: Ingo2711