how to share the photo in photostream from mac mini to iPad

See this: iPhoto and Aperture: Using Photo Stream

iCloud: Photo Stream FAQ

How do I turn on Photo Stream?

Once your devices are up to date and you have set up your iCloud account, it’s easy turn on Photo Stream on any of your devices. Here’s how:

On your iOS devices, go to Settings > iCloud > Photo Stream, and turn on My Photo Stream and Shared Photo Streams.

On your Mac, go to System Preferences > iCloud and select the checkbox for Photo Stream. Click the Options button to verify that both My Photo Stream and Shared Photo Streams are enabled. Then, open iPhoto or Aperture to confirm that My Photo Streamand Shared Photo Streams are turned on in the application you want to use with Photo Stream. You can also adjust your Photo Stream settings in iPhoto or Aperture Preferences.

Regards

Léonie