It ensures protection against the infamous "Lumiose City glitch," which could previously corrupt save files if the game was saved in the outer ring of the city.
Obtain the file from a trusted source like the hShop. Copy the CIA file to your SD card. Open the FBI app on your 3DS. Navigate to the file and select "Install and delete CIA" . pokemon x update 15 cia better
If you are using a standard retail 3DS, you can still download the update by following the Official Nintendo Support guide and scanning the provided QR code. For users with CFW: It ensures protection against the infamous "Lumiose City
For players using emulators like Citra, a CIA file is the required format to manually "install" the update into the emulator environment. pokemon x update 15 cia better