How to Update iLife Applications
If you enabled the Software Update option in your Mac OS X System Preferences, the system automatically informs you of updates to your Apple software for the Mac, including all iLife applications. All you need to do is select which updates to download and then click the Install button to download them.
To enable the Software Update option, choose System Preferences from the Apple menu, click Software Update, and then click the Check for Updates option and choose Daily, Weekly, or Monthly from the pop-up menu.
Mac OS X can automatically run software update checks in the background and let you know when an update is available; simply click the Download Important Updates Automatically option. iLife updates are considered important! With this option, the system automatically notifies you of an update and gives you the option to install it immediately.
When an update appears, you can choose to install it or click Cancel to install it later. After choosing to install the update, you’re prompted for your login password, so make sure that you know the password before trying to install the update.
You can also check for an update of each application from within the application: In iPhoto, choose iPhoto→Check for Updates; in iMovie, choose iMovie→Check for Updates; in iDVD, choose iDVD→Check for Updates; in iWeb, choose iWeb→Check for Updates; and in GarageBand, choose GarageBand→Check for Updates.