1) Open the folder SITE_FLASH and locate folder gallery or images in there.
2) Open the folder images or gallery and see the photos inside – these are all your photos for the gallery
3) Set the correct dimensions for the new images, you can see dimensions in the properties of each image
4) When you have set the correct dimensions for your new image, go back to your SITE_FLASh folder root and open the folder XML
5) Open "main.xml" file with any text editor and locate the list of links for the gallery in there
6) Copy the last line as many times as many images you’ve added and change links in there.
Feel free to check the detailed video tutorial below:XML Flash. How to extend gallery