Search for 'Update' in the iPhoto Help section & you will find this.
Update your iPhoto software
By default, iPhoto automatically notifies you when software updates are available.
If you purchased iPhoto in the Mac App Store, or if iPhoto was pre-installed on your computer along with Mac OS X v10.7 Lion or later, an update notification is displayed on the App Store icon in the Dock.
If you installed iPhoto from the iLife ’11 DVD, or if iPhoto was pre-installed on your computer along with Mac OS X v10.6.8 Snow Leopard or earlier, iPhoto periodically checks for updates when you open iPhoto and notifies you if an update is available. If you don’t want iPhoto to automatically check for updates, you can turn off automatic notifications in iPhoto preferences.
You can also check for updates manually.
Then expand the boxes below it to update your iPhoto based on how it was installed on your mac, and what OS you are running.
For me, running iPhoto on a 2 day old MBP with Lion & iPhoto pre-installed, running the general software updater didn't find the 9.2 update. However, opening the App store & clicking on 'Updates' gave me the option to update to iPhoto 9.2
Mark this right if it helps 🙂