Warning : if you can, make a backup of you release 1.2 database, the script was tested many times, but you never know !

1. download upgrade script : upgrade1.2to1.3.zip
2. extract file upgrade1.2to1.3.php and upload it in the directory "include" of your PhpWebGallery 1.2 installation
3. go the URL (modify it to comply with your installation) http://yourdomain/Gallery/include/upgrade1.2to1.3.php
4. save file include/mysql.inc.php on your local computer
5. delete all files of your PhpWebGallery 1.2 installation BUT directory "galleries"
6. upload PhpWebGallery 1.3 files
7. overwrite the empty include/mysql.inc.php with the one you saved on your local computer

that's all, you can go to your gallery : http://yourdomain/yourGallery