You need to turn on My Photo Stream in iPhoto and on each iOS device that you want to include in your photo stream.
Before you can turn on My Photo Stream, you need to set up your iCloud account on your computer and devices.
Note: To use iCloud, you need an Apple ID. If you don’t have an Apple ID, you can create one during setup.
Open System Preferences and click iCloud.
Type your Apple ID and password, and then click Sign In.
If you don’t have an Apple ID, click “Create an Apple ID” and follow the onscreen instructions.
Select your options and click Next.
Click Done.
Select the Photos checkbox.
To turn on My Photo Stream, click Options next to the Photos checkbox, select the My Photo Stream checkbox, and click OK.
If you choose not to turn on My Photo Stream now, you can turn it on later in iPhoto preferences.
Open iPhoto and select iCloud in the Source list.
Click Use iCloud.
Any new photos that you import into iPhoto are uploaded to iCloud and added to My Photo Stream. By default, photos already in your photo stream (for example, photos added to My Photo Stream by an iOS device) are also automatically imported into your iPhoto library.
To change your settings for adding photos to My Photo Stream or for importing photos into your iPhoto library, choose iPhoto > Preferences and click iCloud. You can also turn My Photo Stream on and off in iPhoto preferences.
Important: My Photo Stream can be associated with only one library at a time. When you switch libraries, iPhoto prompts you to set My Photo Stream to share photos with the new library exclusively. Photos from My Photo Stream and shared photo streams are pushed to the new library from that point on.