Warning: This is an old tutorial, and meant purely for archiving purposes. I wouldn't recommend you follow this

So what is it?
It's a Windows program to convert 3DS roms to CIA files, those CIA files can then be used to install the converted 3DS rom on Gateway or Custom FirmWare (CFW)

It can convert Multiple roms at 1 go :)

Why a guide if it's so simple?
Why are there guides for everything?, for example internet for dummies, etc...
So let's start

What you need

* The latest release of Decrypt9WIP
* slotkey_input.zip
(mirror)
* The latest release of 3DS Simple CIA Converter

Instructions

1. Unzip the rar to wherever you like
2. Copy Decrypt9WIP.bin to luma/payloads/select_Dec9.bin
3. Find your roms you want to convert to CIA and place them in the rom folder
4. Copy the contents of `slotkey_imput.zip`
5. Start "3ds_simple_cia.exe" and choose "Create 'ncchinfo.bin' file" and if you want, check FW Spoof.

- FW Spoof is only needed if your EmuNAND is lower then the Firmware the game needs to run

6. 3ds_simple_cia will ask for a folder, It will automaticly pick the roms folder, so just hit the button folder select NO need to type anything!
7. Then it will ask for a folder where to store the ncchinfo file, just hit the save button again, you don't have to type anything!
8. Now, remove the SD/MicroSD from your (N)3DS(XL) and connect it to your computer
9. Copy ncchinfo.bin to the root of your SD card,
10. Safely remove the sd from your computer and place the sd back in your 3ds and boot into "Decrypt9WIP" by holding L+Select
11. Go to XORpad Generator Option
12. Under XORpad Generator Option select NCCH Padgen
12. When NCCH Padgen says succeeded! you can press B to go back to the main UI and then shut down your 3DS (Hold <-+START),
14. Remove your SD and connect it to your computer.
15. You see multiple xorpads, depends on how many 3DS roms you placed in the "rom" folder. Select ALL xorpads and move them to your xorpads folder where you placed 3ds_simple_cia.exe.
16. Now go back to your 3DS Simple CIA Conveter program (you sure have left open, if not restart it)
17. Select "Convert 3DS ROM to CIA" a windows pop up to select a folder, leave it like it is and press "Select folder". No need to type anything!
18. A few seconds or minutes later you will see a small windows pop up saying "Finished" press "OK" and close the program
19. Now go to your "cia" folder and you will see your converted 3ds roms as cia files
20. Install with FBI