Download Neko_Moonshell.7z.

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

Create a Skins folder in the root of your flashcart’s SD card.

Inside the 7z archive, you will find a folder called Neko_Moonshell.

From this folder, copy Neko_Moonshell.skn to the Skins folder on your SD.

Place the SD card back into your cart, and launch Moonshell 2.

In Moonshell 2, navigate to the Skins folder and press A on Neko_Moonshell.skn to apply the theme.