To upgreade:

1. Upgrade the webapp using

    webapp-config -h <VHOST_HOSTNAME> -d <VHOST_APPDIR> -U gallery X.Y.Z

2. Direct your browser to

    http://<VHOST_HOSTNAME>/<VHOST_APPDIR>/index.php/upgrader

or alternatively, at a shell prompt, run

    php index.php upgrade 

3. Enjoy!

The Gallery 3 user's guide can be found at

    http://codex.galleryproject.org/Gallery3:User_guide:Gallery3:Installing_and_upgrading#Upgrading