Upgrade instructions are located in the documentations folder of our downloaded code. You may unpack the archive and delete the data and uploads directories. You may delete the config php files and install.php file. You may delete the header and footer htm files in the main directory. You then ftp to your server and upload that structure to your photopost directory overwriting whats there. You then run upgrade.php in your browser like so http://www.domain.com/gallery/upgrade.php
You select from your last version forward on that list and run your upgrades. Once your done delete upgrade.php from your server and enjoy. Let me know if you need anything else. Have a great weekend.