To have a successfull update, you must have the version 2.1.2 of PicsEngine. If you have downloaded PicsEngine after the 7th february 2007, it's all good.
First of all, connect you on your FTP. Make a backup of your photos in downloading the folder pictures/. Download also the file config.php in admin/. Delete the whole content of admin/ without erasing the file config.php. Go back to the main directory of PicsEngine, you have some files and the folders admin/ and pictures/. Delete the others files/folders (but not admin/ and pictures/).
Download the ZIP file of PicsEngine 3. When you got it, extract all the files.
Then, upload all files on your server (in most case, you have to use a FTP client).
Be careful to not replace the folder pictures/ and the file admin/config.php!
Imagine you upload the files that appear here http://mywebsite.com/picsengine/.
Open this page on your favorite web browser to begin the update.
You can see a button named "Update from 2.1.2", click on it.
Now you can have this page. It's not sure because, perhaps, all is ok for you the first time.
This page appear if PicsEngine doesn't have write access to some directories. Set the chmod of the directories listed to 777 with your FTP client.
The next step is the MySQL informations. If you always have the admin/config.php file, these informations must be filled.
To avoid any risk, download the database backup by clicking the button. When the download is finished, click on continue.
Click on Continue.