Download Jigoku Shōjo - Hell Girl.7z.

Open/Extract the .7z archive. You can use 7-Zip to do this.

Inside the .7z archive, you will find a folder called Jigoku Shōjo - Hell Girl. Copy this folder to /_pico/themes on your flashcart’s SD card.

Navigate to the _pico folder, and find the settings.json file. Open it with Notepad.

Edit the "theme": line, changing the theme name to Jigoku Shōjo - Hell Girl.

The final edited line in settings.json should look like this: "theme": "Jigoku Shōjo - Hell Girl",

Place the SD card back into your cart, and boot into Pico-Launcher.

The icon/coverflow layout mode is changeable in the Pico-Launcher settings menu. Change it if the theme requires a specific layout.