Custom Firmware (CFW) installed on the console (usually via the popular and Boot9strap method). An SD card reader for your computer. Step-by-Step: How to Generate Your Own aes-keys.txt
A black screen usually indicates that while the emulator found the keys, the specific title key for that exact game is missing or corrupted. Re-dumping the game using GodMode9 as a fully decrypted .3DS file is often the quickest fix for this issue. Conclusion 3ds aes-keys.txt