There are 2 steps to backing up your PhotoStore.
First log in to your management area and go to Settings > Utilities. Next click on the Perform Database Backup button. This will make a backup of your MySQL database. If your database is large or your host has restrictions in place this process may not work so please see below for doing manual database backups.
Next log in through FTP and download all of your files from the directory you have PhotoStore installed in (this includes all php files, the assets directory and the manager directory). Some times this will be public_html but you may also have your PhotoStore installed in a separate directory or your host may have a different setup.
Once you have downloaded all of your files you are all set and now have a backup of your PhotoStore site on your local computer.
To manually back up your MySQL database log in to your hosting control panel and find phpMyAdmin. Load phpMyAdmin and then click on the database that you would like to back up. Next click the "Export" button at the top. Then follow the instructions for saving an export of your database to your local computer.
Handy Backup is an excellent tool for backing up your website. It will connect via FTP and download all of your files at any interval you would like. You can find out more here: http://www.handybackup.net/