$ sudo apt-get update
$ sudo apt-get install imhangul-gtk3 

imhangul-gtk3 is installed in your system.

Make ensure the imhangul-gtk3 package were installed using the commands given below,

$ sudo dpkg-query -l | grep imhangul-gtk3 *

You will get with imhangul-gtk3 package name, version, architecture and description in a table

imhangul-gtk3 package basic information: