1) Choose a source:
The source is a single directory which eventually includes subdirectories. You can select by using the selection panel and then clicking 'add selected' in the source panel.
You can also use the file menu: Source folder - Enter... .
Once you made selections you are recommended to use the quick history menu in the file menu for selecting the same folders again later on!

2) Choose a destination:
Select the destination folder similarly as the source folder.
Remark that the folder that you select is infact the parent folder for the twin. An example:
Suppose you select as source folder
C:\My Documents

... and as destination (parent) folder
C:\My FakeTwinCopies

... then the actual twin will be automatically named something like:
C:\My FakeTwinCopies\faketwin_of_C_-my Documents

3) Hit the run button
The actual twin folder is made now and the subfolder and empty files are created taking into account some options.