If you are on Version 1.0, you can no longer access the Nintendo 3DS eShop (as it has been discontinued) to download the patch officially. However, if you have a modded 3DS or previously downloaded the update data to your SD card before the eShop closure, the game will automatically detect it.
Update 1.4 Pokémon Omega Ruby Alpha Sapphire (ORAS) was a mandatory software patch released by Nintendo and Game Freak. BREATHEcast Pokemon Omega Ruby Update 1.4
Install it only if you plan to use online features or transfer Pokémon to Sun/Moon via Bank. Otherwise, stay on 1.0 – you’re missing nothing fun. If you are on Version 1