Normally after double clicking program executable or shortcut you should see "Open file" dialog where you should select log file for your event:
If that doesn't happen please check that:
- You are running «j3jc.cmd» file from «J3JC>data» folder, not «j3.exe» or «j3jc.ps1»
- Try to press Alt+Tab after black windows has appeared
You should see "Open file" dialog as in the picture above.