$ sudo apt-get update
$ sudo apt-get install fonts-lklug-sinhala-udeb 

fonts-lklug-sinhala-udeb is installed in your system.

Make ensure the fonts-lklug-sinhala-udeb package were installed using the commands given below,

$ sudo dpkg-query -l | grep fonts-lklug-sinhala-udeb *

You will get with fonts-lklug-sinhala-udeb package name, version, architecture and description in a table

fonts-lklug-sinhala-udeb package basic information: