How to update a game?

How to update a game using .cia files???

https://citra-emu.org/wiki/dumping-updates-and-dlcs/ Follow the instructions here.

Actually I wanted to ask if the update was directly applied to the .3ds file

I wanted to transfer the updated .3ds to my android phone for testing it.

the update is installed to the side of the 3ds file, after being dumped as a .cia for installation. So you will have to dump your game, and the update, then place both.

Also, Android version is unofficial and not supported here. We don’t recommend it.