If you want to view a slideshow in another application or on a device such as iPod or iPhone, you first export the slideshow as a QuickTime movie.
To export a slideshow:
Select the slideshow in the Source list. (If you’re in full-screen view, first exit it by clicking Full Screen in the toolbar. If you’re using Mac OS X v10.7 or later, move your pointer to the top of the screen, and then click the Full Screen button that appears in the top-right corner.)
Click the Export button in the toolbar.
You can also choose File > Export, and then click Slideshow.
Depending on the devices you'll use to view your slideshow, select one or more sizes. (For more information, see Export a photo.)
If you don’t want iPhoto to send your slideshow to iTunes (if you don’t plan to use iTunes to sync the slideshow to a device), deselect “Automatically send slideshow to iTunes.”
Sending a slideshow to iTunes enables you to sync the slideshow to a device, such as your iPhone or iPod. It also makes the slideshow available in the Media Browser, so that you can easily insert the slideshow in documents you create in iLife and iWork.
Click the Export button.
Choose a location to save your slideshow and click OK.
If you selected the checkbox in step 4, iTunes opens for you.
To copy your slideshow to a device, see View photos or slideshows on iPod, iPhone, iPad, or Apple TV. (For HDTV, see the manufacturer’s instructions.)