Boot your 3DS into GodMode9 (usually by holding while powering on).
Follow the official guide at 3ds.hacks.guide . This will install Luma3DS and GodMode9. Do not use video tutorials, as they get outdated. The written guide is always current. aes-keys.txt citra
You can avoid needing this file by using already-decrypted .3ds or .cia game files. Boot your 3DS into GodMode9 (usually by holding