How to install custom themes

What is CHMM2 and why shouldn't I use Themely?

CHMM2 is a theme manager for 3DS for custom themes
CHMM2 allows users to apply custom themes by modifying the theme's extdata
However CHMM2 is overall buggy, I recommend using CHMM2 anyways. After some testing it seems like themely cannot handle the fact that I don't have a BGM, which results in a fuzzy sound.

Section I - clearing your extdata

This is an optional step, I always do this but its not required at all

Make sure your Nintendo 3DS is turned off

Always make backups! I am NOT responsible for data loss

1. Remove your SD card from your device, then insert your SD card into your computer
2. Delete the following folders if exist:
sdmc:/Nintendo 3DS/ID/ID/extdata/00000000/000002ce
sdmc:/Nintendo 3DS/ID/ID/extdata/00000000/000002cd
sdmc:/Nintendo 3DS/ID/ID/extdata/00000000/000002cc
3. Reinsert your SD card into your 3DS

Section II - Recreating extdata

1. Open the theme selection menu in HOME-menu-settings
T-thats it...

Section III - Copying custom themes

Make sure your Nintendo 3DS is turned off.

1. Remove your SD card from your device, then insert your SD card into your computer
2. Create a folder called: "themes" on the root of the SD card if not exist already
3. Copy the theme.zip downloaded here or anywhere else to the "themes" folder you just created
4. Reinsert your SD card into your 3DS

Section IV - Installing custom themes

1. Download (and install) CHMM2 if not already
2. Open CHMM2 (Either through the homebrew launcher or the installed CIA)
3. When in CHMM2, use your D-pad to select the theme you want to apply
4. Press A to install theme
5. When installed, press start and select exit CHMM2 to return

Congrats! you now have a custom theme!

If you want to install new themes I recommend starting from Section III again