$ sudo apt-get update
$ sudo apt-get install libckit-smlnj 

libckit-smlnj is installed in your system.

Make ensure the libckit-smlnj package were installed using the commands given below,

$ sudo dpkg-query -l | grep libckit-smlnj *

You will get with libckit-smlnj package name, version, architecture and description in a table

libckit-smlnj package basic information: