You don't need an EmuNAND, it's not worth the gigabyte, as you can simply replace the SysNAND if you need to, rendering it useless and outdated for the average user really.
If you're like me and don't care and wanna make one anyways, then backup your entire SD card onto your computer. Do not skip this step.
Then boot into GodMode9 with your 3DS, Press Home > More... > SD Format Menu > either "O3DS NAND size" or "N3DS NAND size" > whatever options are next (I'm not risking formatting my SD card just for the example lol).
Then after that is done, press R+B to unmount your SD card, put it back into your computer, copy the SD card files you backed up earlier back onto the SD card, put it back in the system, and reboot.
That should be how you do it, iirc. That's how I got mine setup anyways.
You can check what NAND you're on by going to System Settings, it should either say "Sys" or "Emu" by the version number.
If you wanna coldboot into the EmuNAND, power off the system, and boot it up again holding "Select", and then enable:
(x) Autoboot EmuNAND
Press Start to save and reboot. If you wanna boot back into SysNAND with that option enabled, just hold L on boot.
Hope that helps. ^^
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