Warning: Piracy sites offer pre-decrypted CIAs. Installing these on a real 3DS requires disabling signature checks via Luma3DS. Keep your console offline if you use unofficial updates to avoid a ban.
: Go to File > Install CIA... and select your decrypted update file. pokemon x update 15 decrypted 3ds eur usa
The 3DS is region-locked. This means a USA console cannot play EUR games natively, and the update files are specific to the region of the game cartridge. Warning: Piracy sites offer pre-decrypted CIAs