This is taken from http://www.endymios.com/flash-gallery-module and modified a bit:

  • Download flash gallery module and copy it to your modules directory
  • Download Simpleviewer from Airtight Interactive. Unzip the package.
  • Create a new directory inside the flash_gallery directory in your modules directory called ’simpleviewer’ (modules/flash_gallery/simpleviewer/).
  • Copy ’swfobject.js’ and ‘viewer.swf’ to the simpleviewer directory. Do not copy any other files from the Simpleviewer package.
  • Make sure that you have image.module and image_gallery.module enabled before you enable flash_gallery.module.
  • Enable the module @ admin > modules
  • Change the settings @ admin > settings > flash galleries
  • Create a image gallery
  • Copy image files into the importer folder, and then import all the images into the gallery
  • Check ‘build thumbnail library’ in the miscellaneous section and hit save
  • Navigate to http://yoursite.com/fgallery to see the module in action
  • Suggestion: set a path alias for fgallery
  • Suggestion: disable all blocks on fgallery /* as this will give you more space to display your albums

Simple Viewer can also be used separately, here is the tutorial.