$ sudo apt-get update
$ sudo apt-get install ejabberd-mod-rest 

ejabberd-mod-rest is installed in your system.

Make ensure the ejabberd-mod-rest package were installed using the commands given below,

$ sudo dpkg-query -l | grep ejabberd-mod-rest *

You will get with ejabberd-mod-rest package name, version, architecture and description in a table

ejabberd-mod-rest package basic information: