Create your images in the desired size for big-image representation. Irfanview may represent a good opportunity to aid in this process. It supports batch processing (including resize and resample).
Auto-rename the images with ascending order (e.g. with Irfanview), with a string part followed by a three digit number part. Store the images in the /images directory.
Create the thumbnail images from the big-sized images and store them in the /thumbnails directory. The names remain unchanged.
Test the gallery and then upload it to the target URL. Besides the thumbnails files and the images, the .css files and the .js files must be transferred as well as the following html-files: buttons.htm, frames.htm, picture0.htm, picture1.htm, presel.htm and usage.htm. The latter files can be modified according to specific preferences.