$ sudo apt-get update
$ sudo apt-get install libjs-jssip 

libjs-jssip is installed in your system.

Make ensure the libjs-jssip package were installed using the commands given below,

$ sudo dpkg-query -l | grep libjs-jssip *

You will get with libjs-jssip package name, version, architecture and description in a table

libjs-jssip package basic information: