STOP EVERYONE!
I feel like I know more about this topic, and the guide Poke J linked is quite outdated. Why do you want an Emunand exactly? That should be the first question since what suits you best depends on that.
The recommended method is to install A9LH and don't use EMUNand at all. For that follow this guide: https://3ds.guide/
Some notes about current A9LH installation:
- You do a full nand backup before the process starts. You should keep at least 2 copies of that somewhere safe (different hard disks) since this nand backup can be used to restore your 3DS to exactly how it was before you installed A9LH, used CFW or anything.
- A9LH allows you to directly boot into CFW EMUNand way faster than other methods.
- A9LH can be uninstalled without restoring a nand backup, so you might install A9LH to use an emunand and leave your SYSNand untouched (except for A9LH installation) and remove it anytime you want. If you don't use EMUNand and install a crapload of things to your sysnand over the months and at some point you want to "unmodify" your 3DS, the best way is to restore your Nand backup, since that gets you back where you started.
IMPORTANT: if you suspend (close the lid) of your console during A9LH installation you will brick it. This is the only significant danger in A9LH installation, since the programs have many safety checks to ensure everything goes fine.
Boot process on A9LH + Luma CFW (the recommended cfw):
- Power ON (and that's all, you can now access everything)
If you want EMUNand because you have a 9.0<->11.3 firmware console and you want to leave your SYSNand untouched, you can run EMUNand from homebrew launcher and you never have to install anyhting on your 3DS, but the boot process is tedious and longer, but valid if you are afraid of messing up A9LH installation. I don't have link for a guide for this method, but it is possible to do it this way. On firmwares that have menuhax you can speed up the boot process, menuhax sometimes fails.
The boot process for Emunand on untouched sysnand would be:
- Power ON
- Use entrypoint to get on homebrew launcher (depends on firmware)
- Run fasthax (or the alternative for 11.3 that came out recently)
- Run the kernel exploit (safehax I believe)
- Run the EMUNand launcher (I believe just Luma CFW launcher at this point)
- Wait until EMUNand boots.
To setup an emunand you just need to use Emunand9 under kernel access, (BACKUP YOUR SD CARD FIRST! CONTENTS GET ERASED AND YOU HAVE TO COPY THEM OVER AFTER SETUP!): https://gbatemp.net/threads/release-emunand9-open-source-emunand-formatter-manager.405921/
Emunand9 basically formats your SD card, makes the emunand partition and copies your sysnand over to the emunand partition ready to be boot with a CFW like Luma. Afterwars you just need to copy the contents you backed up from your SD card again onto the SD card.
ps: all homebrew in the most updated version have many safety checks to ensure nothing goes wrong, but doing things with kernel access always means there's a chance something goes wrong (normally due to the user doing something wrong/skipping some steps) and bricking your 3DS.