Hopefully it runs on your system.
To start, double click jvtgui.dist/run_jvtgui.bat.
On Linux we have jvtgui.dist/run_jvtgui.sh. This project should be cross-platform.
Try editing that file too by uncommenting appropriate lines.
Remember to comment the ones you don't want to use.
Take a look at the start file for Linux (run_jvtgui.sh) for more commentary.
Configuration files and downloads are stored in ~/.jvt/Downloads.
For me that would be C:/Users/spike/.jvt. Open that and poke around.
In the future I'll add an option for customizing the theme in the settings.json file.