$ sudo apt-get update
$ sudo apt-get install juju-1-default 

juju-1-default is installed in your system.

Make ensure the juju-1-default package were installed using the commands given below,

$ sudo dpkg-query -l | grep juju-1-default *

You will get with juju-1-default package name, version, architecture and description in a table

juju-1-default package basic information: