Installing Pokémon X Update 15 decrypted 3DS EUR/USA requires a few steps:
The Pokémon X Update 1.5 CIA file matching your game's region. USA Region ID: 0004000000055D00 EUR Region ID: 0004000000055E00 pokemon x update 15 decrypted 3ds eur usa install
If you are using a ROM hack like Pokémon Neo X , the creator explicitly states that you have version 1.5 installed for the hack to function correctly. Installing Pokémon X Update 15 decrypted 3DS EUR/USA