MacBook Pro

Welcome to Apple Support Communities

You have Lion, and Notification Center is included with Mountain Lion. You can use a third-party application like Growl to get notifications for some apps > http://growl.info

The other option is to upgrade to Mountain Lion, so open the App Store and purchase Mountain Lion. While it's being downloaded, make a backup of your data and check that your applications are supported > http://www.roaringapps.com

When the download finishes, the Mountain Lion installer will appear, so follow the steps. After upgrading, you will be able to go to System Preferences > Notifications. Read > http://support.apple.com/kb/HT5362

Marilyn,

Notifications were introduced in MAc OS X 10.8. If you signature is correct then you are running Mac OS X 10.7.