this guide links to both Cakes and AuReiNAND, I recommend using AuReiNAND. switching is easy
https://github.com/Plailect/Guide/wiki/Part-5-(arm9loaderhax-&-AuReiNAND)
Follow these steps only (under Preparatory Work)
Step 1
Step 7 (this will help you run Homebrew Launcher as a CIA, skip if you have done this already)
Step 8 (if you have files here, delete all files and folders except firmware90.bin (if you have this)
Step 9
Step 10
Step 11
Step 13
Step 14
Step 15
Step 16
Step 17
Step 18
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Next, follow all the steps from Configuring AuReiNAND (
VERY IMPORTANT)
if you need to get back into this menu, hold select and press power button while console is off
That is it, you are done upgrading AuReiNAND to latest and have enabled FIRM protection so you can safely update SysNAND without bricking.
To run 3DSX homebrew, use DevMenu or FBI to install the Homebrew Launcher CIA from step 7 that you copied to your SD Card.
Here is a link to the homebrew menu starter package in case you do not have this
http://smealum.github.io/ninjhax2/starter.zip
This is needed to use the homebrew launcher CIA properly
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What you can do with a9lh and AuReiNAND (copy and paste from guide)