Here's how it works:
1) Open the "app.config" file for editing
2) Specify the input directory, where you have your ENGLISH .resx-files.
e.g. "C:\My Project\App_LocalResources\en-US"
3) Specify the output directory - this should be the !!RELATIVE!! path to the input directory
e.g. ".." (recommended value is "..")
4) Specify if you want the program to create a separate folder for each output language.
I.e. if you translate to Spanish and French - the program will create two folders: "es-ES" and "fr-FR".
Recommended setting is "true".
5) Run the program.